ABINIT, developper input variables:

List and description.


This document lists and provides the description of the name (keywords) of the input variables "for developpers" to be used in the main input file of the abinit code.

Content of the file : alphabetical list of developper variables.


A.
B. builtintest  
C. cgtyphf  
D. densfor_pred   densty   dmft_dc   dmft_entropy   dmft_iter   dmft_mxsf   dmft_nlambda   dmft_nwli   dmft_nwlo   dmft_read_occnd   dmft_rslf   dmft_solv   dmft_t2g   dmft_tolfreq   dmft_tollc   dmftbandf   dmftbandi   dmftcheck   dmftctqmc_basis   dmftctqmc_check   dmftctqmc_correl   dmftctqmc_gmove   dmftctqmc_grnns   dmftctqmc_meas   dmftctqmc_mov   dmftctqmc_mrka   dmftctqmc_order   dmftctqmc_triqs_nleg   dmftqmc_l   dmftqmc_n   dmftqmc_seed   dmftqmc_therm  
E. effmass   eshift   exchmix   exchn2n3d   extrapwf  
F. fermie_nest   fftalg   fftcache  
G. getgam_eig2nkq   getwfkfine  
H.
I. intxc   iomode   iprcfc   irandom   irdvdw   irdwfkfine   isecur   istatr   istatshft   istwfk  
J.
K.
L. lotf_classic   lotf_nitex   lotf_nneigx   lotf_version  
M. macro_uj   maxnsym   mem_test   mqgrid  
N. nbdblock   nc_xccc_gspace   nctime   nloc_alg   nloc_mem   nnsclo   nnsclohf   normpawu   npulayit   nscforder  
O. optforces   optnlxccc   ortalg  
P. papiopt   pawprt_b   pawprt_k   pawujat   pawujrad   pawujv   plowan_bandf   plowan_bandi   plowan_compute   plowan_iatom   plowan_it   plowan_lcalc   plowan_natom   plowan_nbl   plowan_nt   plowan_projcalc   plowan_realspace   prepscphon   prtbltztrp   prtcif   prtdipole   prtnest   prtposcar   prtvdw  
Q.
R. recefermi   recgratio   recnpath   recnrec   recptrott   recrcut   rectesteg   rectolden  
S. symmorphi  
T. tfkinfunc   tfw_toldfe   tolrde  
U. use_gemm_nonlop   use_nonscf_gkk   usedmft   useria   userib   useric   userid   userie   userra   userrb   userrc   userrd   userre   useylm  
V. vdw_df_acutmin   vdw_df_aratio   vdw_df_damax   vdw_df_damin   vdw_df_dcut   vdw_df_dratio   vdw_df_dsoft   vdw_df_gcut   vdw_df_ndpts   vdw_df_ngpts   vdw_df_nqpts   vdw_df_nrpts   vdw_df_nsmooth   vdw_df_phisoft   vdw_df_qcut   vdw_df_qratio   vdw_df_rcut   vdw_df_rsoft   vdw_df_threshold   vdw_df_tolerance   vdw_df_tweaks   vdw_df_zab   vdw_nfrag   vdw_supercell   vdw_tol   vdw_tol_3bt   vdw_typfrag   vdw_xc  
W. wfoptalg  
X. xc_denpos   xc_tb09_c  





builtintest
Mnemonics: BUIT-IN TEST number
Characteristic: DEVELOP
Variable type: integer
Default is 0

When builtintest is non-zero, the input file is a special one, that runs very quickly, and that is accompanied by a specific analysis by ABINIT, at the end of the run, against a hard-coded value of total energy (and possibly stresses, forces ...). The echo of the analysis is done in the STATUS file. In particular, such built-in tests can be used to check quickly whether ABINIT fallbacks have been connected or not (bigdft, etsf_io, libxc, wannier90). At present, builtintest=1 ... 7 are allowed. See more information in tests/built-in/README .





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cgtyphf
Mnemonics: Conjugate Gradient TYpe used for Hartree Fock exact exchange
Characteristic: DEVELOP
Variable type: integer
Default is 2 if usefock == 1, 0 otherwise.

Gives how is calculated Fock exact exchange contribution in the conjugate gradient, in the SCF case.
The value 2 corresponds to calculate the Fock exact exchange contribution each time in the conjugate gradient. The value 1 corresponds to calculate the Fock exact exchange contribution only for the initial guess (not for the gradient direction) in the conjugate gradient





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densfor_pred
Mnemonics: DENSity and FORces PREDictor
Characteristic: DEVELOP
Variable type: integer
Default is 3 if ionmov==4 and iscf==5, 6 if paral_kgb==1, 2 otherwise.

Only relevant if iscf >0

Used when iscf>0, to define:
- the way a change of density is derived from a change of atomic position,
- the way forces are corrected when the SCF cycle is not converged.

Supported values :

No meaning for RF calculations.

For the time being,
- the choice 3 must be used with ionmov=4 and iscf=5.
- the choices 4, 5 or 6 must be used when band-FFT parallelism is selected.
Otherwise, use the choice 2.

(*) Note concerning the use of densfor_pred=4 or 6 (correction of forces) :
The force on the atom located at R is corrected by the addition of the following term:
F_residual=Int[dr.V_residual.dRho_atomic/dR] , where Rho_atomic is an atomic (spherical) density.
- When such an atomic density (Rho_atomic) is found in the pseudopotential or PAW file, it is used. If not, a gaussian density (defined by densty parameter) is used.
- When SCF mixing is done on the density (iscf>=10), the potential residual (V_residual) is obtained from the density residual with the first order formula V_residual=dV/drho.Rho_residual and uses the exchange-correlation kernel dVxc/drho=Kxc which computation is time-consuming for GGA functionals. By default the LDA exchange-correlation kernel is used (even for GGA, for which it seems to give a reasonable accuracy). Using the exact GGA exchange correlation kernel is always possible by giving a negative value to densfor_pred.

(**) Note concerning the use of densfor_pred=5 or 6 (density prediction) :
The algorithm is described in Computer Physics Communications 118 (1999) 31-33 . It uses an atomic (spherical) density. When such an atomic density is found in the pseudopotential or PAW file, it is used. If not, a gaussian density (defined by densty parameter) is used.
Also note that, to be efficient, this algorithm requires a minimum convergence of the SCF cycle; Typically, vres2 (or nres2) has to be small enough (10 -4 ...10 -5 ).





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densty
Mnemonics: initial DENSity for each TYpe of atom
Characteristic: DEVELOP
Variable type: real(ntypat)
Default is 0.0

Gives a rough description of the initial GS density, for each type of atom. This value is only used to create the first exchange and correlation potential, and is not used anymore afterwards. For the time being, it corresponds to an average radius (a.u.) of the density, and is used to generate a gaussian density. If set to 0.0d0, an optimized value is used.
No meaning for RF calculations.





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dmft_dc
Mnemonics: Dynamical Mean Fied Theory: Double Counting
Characteristic: DEVELOP
Variable type: integer
Default is 1


Value of double counting used for DMFT. Only value 1 is activated for the moment and is the FLL double counting.





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dmft_entropy
Mnemonics: Dynamical Mean Fied Theory: ENTROPY
Characteristic:
Variable type: integer
Default is 0

Only relevant if usedmft==1 and dmft_solv==5

If 1, enable the calculation of the entropy within the DMFT framework and so allows the calculation of the total energy (free energy). In the current implementation, this is only possible with dmft_solv=5 (Continuous Time Quantum Monte Carlo). See also the input variable dmft_nlambda.



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dmft_iter
Mnemonics: Dynamical Mean Fied Theory: number of ITERation
Characteristic: DEVELOP
Variable type: integer
Default is 0


Number of iterations for the DMFT inner loop.





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dmft_mxsf
Mnemonics: Dynamical Mean Fied Theory: MiXing parameter for the SelF energy
Characteristic: DEVELOP
Variable type: real
Default is 0.3


Mixing parameter for the simple mixing of the self-energy.





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dmft_nlambda
Mnemonics: Dynamical Mean Fied Theory: Number of LAMBDA points
Characteristic: DEVELOP
Variable type: integer
Default is 6

Only relevant if usedmft==1 and dmft_entropy==1

dmft_nlambda gives the number of integration points for the thermodynamical integration in case of free energy calculation within DMFT. Its value must be greater or equal to 3.



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dmft_nwli
Mnemonics: Dynamical Mean Fied Theory: Number of frequency omega (W) in the LInear mesh
Characteristic: DEVELOP
Variable type: integer
Default is 0


Number of Matsubara frequencies (linear mesh)





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dmft_nwlo
Mnemonics: Dynamical Mean Fied Theory: Number of frequency omega (W) in the log mesh
Characteristic: DEVELOP
Variable type: integer
Default is 0


Number of frequencies in the log mesh.





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dmft_read_occnd
Mnemonics: Dynamical Mean Fied Theory: Read Occupations (Non Diagonal)
Characteristic: DEVELOP
Variable type: integer
Default is 0


Flag to read/write Occupations as computed in DMFT. This flag is useful to restart a DFT+DMFT calculation with self-consistency over electronic density. The occupations are written each time a DMFT loop is finished. So if the calculation stops because the time limit is reached, this option offers the possibility to restart the self-consistent loop over density at the point where it stopped (assuming a restart with the wave functions, see getwfk).

An alternative and more simple way to restart a DFT+DMFT calculation is to use the density file (obtained with prtden=1 or prtden=-1) and the self-energy (see dmft_rslf).





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dmft_rslf
Mnemonics: Dynamical Mean Fied Theory: Read SeLF energy
Characteristic: DEVELOP
Variable type: integer
Default is 0

Flag to read/write Self-Energy. If put to one, self-energy is written and read at each DFT iteration.





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dmft_solv
Mnemonics: Dynamical Mean Fied Theory: choice of SOLVer
Characteristic: DEVELOP
Variable type: real
Default is 5


Choice of solver for the Impurity model.


The CT Hyb algorithm is described in Phys. Rev. Lett 97, 076405, (2006) . For a discussion of density-density approximation with respect with the rotationnally invariant formulation, see e.g. Phys. Rev. B 86, 155107 (2012) .
The ABINIT/CT Hyb implementation is discussed in http://dx.doi.org/10.1016/j.cpc.2016.04.003 .
The TRIQS/CT Hyb implementation is described in Comp. Phys. Comm. 200, 274 (2016) . Before using it, it has to be installed following instructions at https://triqs.ipht.cnrs.fr/1.3/applications/cthyb/install.html. The current interface is valid for TRIQS 1.3 and TRIQS/CTHYB 1.3.
See the useful variables for CT-QMC solver : dmftctqmc_basis, dmftctqmc_check, dmftctqmc_correl, dmftctqmc_gmove, dmftctqmc_grnns, dmftctqmc_meas, dmftctqmc_mrka, dmftctqmc_mov, dmftctqmc_order, dmftctqmc_triqs_nleg, dmftqmc_l, dmftqmc_n, dmftqmc_seed, dmftqmc_therm





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dmft_t2g
Mnemonics: Dynamical Mean Fied Theory: t2g orbitals
Characteristic: DEVELOP
Variable type: integer
Default is 0


Can be set to 1 only if in cubic symmetry. It enables one to carry a DFT+DMFT calculations only on t2g orbitals.





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dmft_tolfreq
Mnemonics: Dynamical Mean Fied Theory: Tolerance on LDA correlated electron occupation matrix for the definition of the frequency grid
Characteristic: DEVELOP
Variable type: real
Default is 0.0001


The LDA occupation matrix for correlated electrons can be computed directly. It can be compared to the calculation of the same quantity using LDA Green's function, a sum over Matsubara frequencies and a projection over correlated orbitals. Because the Matsubara grid is finite, the two quantities differ. If this difference is larger than dmft_tolfreq, then the code stops and an error message is given.





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dmft_tollc
Mnemonics: Dynamical Mean Fied Theory: Tolerance on Local Charge for convergence of the DMFT loop
Characteristic: DEVELOP
Variable type: real
Default is 1e-05


Tolerance for the variation of Local Charge during iterations of the DMFT Loop.
The default value is good for fast calculations. However, to obtain good convergence of the DFT Loop, the DMFT Loop needs a better convergence criterion.





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dmftbandf
Mnemonics: Dynamical Mean Field Theory: BAND: Final
Characteristic: DEVELOP
Variable type: integer
Default is 0

dmftbandf is the last band taken into account in the Projected Local Orbitals scheme of DFT+DMFT. With dmftbandi, they define the energy window used to define Wannier Functions. (see Amadon, B., Lechermann, F., Georges, A., Jollet, F., Wehling, T. O., and Lichtenstein, A. I. Phys. Rev. B 77(20), (2008).)





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dmftbandi
Mnemonics: Dynamical Mean Field Theory: BAND: Initial
Characteristic: DEVELOP
Variable type: integer
Default is 0

dmftbandi is the first band taken into account in the Projected Local Orbitals scheme of LDA+DMFT. With dmftbandf, they define the energy window used to define Wannier Functions. (see Amadon, B., Lechermann, F., Georges, A., Jollet, F., Wehling, T. O., and Lichtenstein, A. I. Phys. Rev. B 77(20), (2008).)





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dmftcheck
Mnemonics: Dynamical Mean Fied Theory: CHECKs
Characteristic: DEVELOP
Variable type: integer
Default is 0


Only for developer purposes. (Introduced by B. Amadon, v6.1.0)





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dmftctqmc_basis
Mnemonics: Dynamical Mean Fied Theory: Continuous Time Quantum Monte Carlo basis
Characteristic: DEVELOP
Variable type: integer
Default is 1

Only relevant if dmft_solv==5


Choose the basis to perform CTQMC calculation.





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dmftctqmc_check
Mnemonics: Dynamical Mean Fied Theory: Continuous Time Quantum Monte Carlo check
Characteristic: DEVELOP
Variable type: integer
Default is 0

Only relevant if dmft_solv==5


Check the fast calculations during the Monte Carlo simulation with very slow but robust methods. Should only be used for debugging.





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dmftctqmc_correl
Mnemonics: Dynamical Mean Fied Theory: Continuous Time Quantum Monte Carlo CORRelations
Characteristic: DEVELOP
Variable type: integer
Default is 0

Only relevant if dmft_solv==5


Flag to compute statistics about segments and anti-segments during the simulation. Slow down the simulation.





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dmftctqmc_gmove
Mnemonics: Dynamical Mean Fied Theory: Continuous Time Quantum Monte Carlo Global MOVEs
Characteristic: DEVELOP
Variable type: integer
Default is 0

Only relevant if dmft_solv==5


Default is no global moves. The value of this variable is the modulo used to try a global move. A value of 5000 means that a global move is tried every 5000 Monte Carlo sweep.





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dmftctqmc_grnns
Mnemonics: Dynamical Mean Fied Theory: Continuous Time Quantum Monte Carlo GReeNs NoiSe
Characteristic: DEVELOP
Variable type: integer
Default is 0

Only relevant if dmft_solv==5


Compute the statistical noise for each time slice of each green function. This is a good approximation only if there is enough Monte Carlo sweeps per cpu.





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dmftctqmc_meas
Mnemonics: Dynamical Mean Fied Theory: Continuous Time Quantum Monte Carlo MEASurements
Characteristic: DEVELOP
Variable type: integer
Default is 1

Only relevant if dmft_solv==5


The modulo used to measure the interaction energy and the number of electrons. Example : 2 means the measure is perform every two sweeps.





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dmftctqmc_mov
Mnemonics: Dynamical Mean Fied Theory: Continuous Time Quantum Monte Carlo MOVie
Characteristic: DEVELOP
Variable type: integer
Default is 0

Only relevant if dmft_solv==5


Print a latex file per cpu displaying the full simulation. This option should only be use with very small number (<1000) of Monte Carlo sweeps since it requires a lot of I/O band width.





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dmftctqmc_mrka
Mnemonics: Dynamical Mean Fied Theory: Continuous Time Quantum Monte Carlo MARKov Analysis
Characteristic: DEVELOP
Variable type: integer
Default is 0

Only relevant if dmft_solv==5


Measure the time evolution of the number of electrons for each orbital and perform a fourier transform. The result can be plotted using the "Markov_id.dat" file





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dmftctqmc_order
Mnemonics: Dynamical Mean Fied Theory: Continuous Time Quantum Monte Carlo perturbation ORDER
Characteristic: DEVELOP
Variable type: integer
Default is 0

Only relevant if dmft_solv==5


Print a file containing the statistic distribution of the number of segments per orbital. The maximal order taken into account dmftctqmc_order : 50 means that we have the statistic distribution from 0 to 50 segments. The result is written in the "Perturbation.dat" file.





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dmftctqmc_triqs_nleg
Mnemonics: Dynamical Mean Fied Theory: Continuous Time Quantum Monte Carlo perturbation of TRIQS, Number of LEGendre polynomials
Characteristic: DEVELOP
Variable type: integer
Default is 30

Only relevant if dmft_solv==6 or 7


Specify the number of Legendre polynomials used for the calculation of Green's function in CTQMC code from the library TRIQS. Default is 30. The value of coefficients are given in file whose name ending is "Legendre_coefficient.dat". (see also Phys. Rev. B 84, 075145 (2010))





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dmftqmc_l
Mnemonics: Dynamical Mean Fied Theory: Quantum Monte Carlo time sLices
Characteristic: DEVELOP
Variable type: integer
Default is 0

Only relevant if dmft_solv>=4


Number of time slices used to represent the time green function. This value should be carefully chosen according to Niquist frequency and the tsmear value.





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dmftqmc_n
Mnemonics: Dynamical Mean Fied Theory: Quantum Monte Carlo sweeps
Characteristic: DEVELOP
Variable type: real
Default is 0.0

Only relevant if dmft_solv>=4


Number of Monte Carlo sweeps. Should be at least 10^6.





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dmftqmc_seed
Mnemonics: Dynamical Mean Fied Theory: Quantum Monte Carlo seed
Characteristic: DEVELOP
Variable type: integer
Default is jdtset

Only relevant if dmft_solv>=4


Seed to initilize the random number generator.
Should not be relevant except for testing purpose.
NOTE : If the CT-QMC (dmft_solv=5) is used on many CPUs, each CPU initializes its random number generator with dmftqmc_seed+rank where rank is the rank of the cpu in the MPI communicator.





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dmftqmc_therm
Mnemonics: Dynamical Mean Fied Theory: Quantum Monte Carlo THERMalization
Characteristic: DEVELOP
Variable type: integer
Default is 1000

Only relevant if dmft_solv==5


Number of Monte Carlo sweeps for the thermalization





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effmass
Mnemonics: EFFective MASS
Characteristic: DEVELOP
Variable type: real
Default is 1


This parameter allows to change the electron mass, with respect to its experimental value.





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eshift
Mnemonics: Energy SHIFT
Characteristic: DEVELOP, ENERGY
Variable type: real
Default is 0

Only relevant if wfoptalg==3

eshift gives the shift of the energy used in the shifted Hamiltonian squared. The algorithm will determine eigenvalues and eigenvectors centered on eshift.
Can be specified in Ha (the default), Ry, eV or Kelvin, since ecut has the 'ENERGY' characteristics. (1 Ha=27.2113845 eV)





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exchmix
Mnemonics: EXCHange MIXing
Characteristic: DEVELOP
Variable type: real
Default is 0.25

Only relevant if useexexch == 1

exchmix allows to tune the ratio of exact exchange when useexexch is used. The default value of 0.25 corresponds to PBE0.





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exchn2n3d
Mnemonics: EXCHange N2 and N3 Dimensions
Characteristic: DEVELOP
Variable type: integer
Default is 0

If exchn2n3d is 1, the internal representation of the FFT arrays in reciprocal space will be array(n1,n3,n2), where the second and third dimensions have been switched. This is to allow to be coherent with the exchn2n3d=4xx FFT treatment.





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extrapwf
Mnemonics: flag - EXTRAPolation of the Wave-Functions
Characteristic: DEVELOP
Variable type: integer
Default is 0

Only relevant if densfor_pred==5 or densfor_pred==6

This flag activates the extrapolation of wave-functions from one Molecular Dynamics (or Structural Relaxation) step to another. The wave functions are extrapolated using 2nd-order algorithm of Arias, Payne and Joannopoulos (PRB 45, 1538 (1992)).
Note that, when activated, this extrapolation requires non-negligible additional memory resources as the wave functions are stored for the two previous time steps. Also, it can only be activated if a consistent density extrapolation is activated (see densfor_pred).
ABINIT 7.10: this option is under development and might give wrong results.





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fermie_nest
Mnemonics: FERMI Energy for printing the NESTing function
Characteristic:
Variable type: real
Default is 0

This input variable is only effective when prtnest=1. The energy is relative to the calculated fermi energy.





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fftalg
Mnemonics: Fast Fourier Transform ALGorithm
Characteristic: DEVELOP
Variable type: integer
Default is 312 if FFTW3 and usedmft==0, 401 if paral_kgb==1, 112 otherwise.

This keyword is irrelevant when Fast Fourier Transforms are done using Graphics Processing Units (GPU), i.e. when use_gpu_cuda=1 (in that case, it is ignored).

Allows to choose the algorithm for Fast Fourier Transforms. These have to be used when applied to wavefunctions (routine fourwf.F90), as well as when applied to densities and potentials (routine fourdp.F90). Presently, it is the concatenation of three digits, labelled (A), (B) and (C).

The first digit (A) is to be chosen among 1, 2, 3 and 4 :

The second digit (B) is related to fourdp.f : The third digit (C) is related to fourwf.f : Internal representation as ngfft(7).





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fftcache
Mnemonics: Fast Fourier Transform CACHE size
Characteristic: DEVELOP
Variable type: integer
Default is 16 (Comment: todo: Not yet machine-dependent)

Gives the cache size of the current machine, in Kbytes.
Internal representation as ngfft(8).





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getgam_eig2nkq
Mnemonics: GET the GAMma phonon data EIG2NKQ from dataset
Characteristic:
Variable type: integer
Default is 0

Only relevant if ieig2rf != 0 and qpt != (0.0,0.0,0.0)

Relevant for second-order eigenvalue calculations using response-functions (ieig2rf != 0), and only for non-zero wavevectors qpt.
From the electron-phonon matrix elements at some wavevector only, it is not possible to determine the Debye-Waller contribution : one has to know also the q=Gamma electron-phonon matrix elements.
The variable getgam_eig2nkq allows to transmit the information about the second-order derivatives of the eigenvalues for q=Gamma from the dataset where the calculation at Gamma was done, to the datasets for other wavevectors.





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getwfkfine
Mnemonics: GET the fine grid wavefunctions from _WFK file
Characteristic:
Variable type: integer
Default is 0

Eventually used when ndtset>0 (in the multi-dataset mode), to indicate starting wavefunctions, as an alternative to irdwfkfine. One should first read the explanations given for these latter variables.
The getwfkfine variables is typically used to chain the calculations in the multi-dataset mode, since they describe from which dataset the OUTPUT wavefunctions are to be taken, as INPUT wavefunctions of the present dataset.
If getwfkfine==0, no use of previously computed output wavefunction file appended with _DSx_WFK is done.
If getwfkfine is positive, its value gives the index of the dataset for which the output wavefunction file appended with _WFK must be used.
If getwfkfine is -1, the output wf file with _WFK of the previous dataset must be taken, which is a frequently occurring case.
If getwfkfine is a negative number, it indicates the number of datasets to go backward to find the needed wavefunction file. In this case, if one refers to a non existent data set (prior to the first), the wavefunctions are not initialised from a disk file, so that it is as if getwfkfine=0 for that initialisation. Thanks to this rule, the use of getwfkfine -1 is rather straightforward : except for the first wavefunctions, that are not initialized by reading a disk file, the output wavefunction of one dataset is input of the next one.
NOTE : a negative value of a "get" variable indicates the number of datasets to go backwards; it is not the number to be subtracted from the current dataset to find the proper dataset. As an example :

 ndtset 3   jdtset 1 2 4  getXXX -1
refers to dataset 2 when dataset 4 is initialized. Response-function calculation : Bethe-Salpeter calculation : This variable is experimental. In development.




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intxc
Mnemonics: INTerpolation for eXchange-Correlation
Characteristic: DEVELOP
Variable type: integer
Default is 0


For RF calculations only intxc=0 is allowed yet. Moreover, the GS preparation runs (giving the density file and zero-order wavefunctions) must be done with intxc=0

Prior to ABINITv2.3, the choice intxc=1 was favoured (it was the default), but the continuation of the development of the code lead to prefer the default intxc=0 . Indeed, the benefit of intxc=1 is rather small, while making it available for all cases is a non-negligible development effort. Other targets are prioritary... You will notice that many automatic tests use intxc=1. Please, do not follow this historical choice for your production runs.





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iomode
Mnemonics: IO MODE
Characteristic: DEVELOP
Variable type: integer
Default is 1 if MPI_IO and paral_kgb==1, 0 otherwise.

This option selects the format used to produce the output wavefunction files and the files containing densities and potentials. It mainly affects the creation of the output files since several parts of Abinit are able to read data from files independently of their format (either binary files or netcdf files). The possible values are:


By default, Abinit produces Fortran files and uses parallel MPI-IO under the hood when these operations cannot be implemented in terms of simple Fortran write/read statements. For example, paral_kgb=1 uses the MPI-IO API provided by your MPI library.

In a nutshell, use the default value and make sure that your MPI library supports MPI-IO before embarking yourself in large parallel runs (HAVE_MPI_IO should be set to 1 in ~abinit/config.h). Many MPI libraries, nowadays, support the MPI-2 standard so it's very likely that your MPI supports parallel IO. If you encounter problems, please ask your sysadmin to install a MPI library with MPI-IO capabilities.

There are cases, however, in which you would like to change the default behaviour. For example, you may want to generate WFK or DEN files in etsf-io format because you need data in this format. In this case, you have to use iomode==3 in the input file to override the default behaviour. Note however that you still need parallel IO capabilities enabled in the netcdf library if you want to produce netcdf files in parallel with paral_kgb=1 (i.e. netcdf4 + hdf5 + MPI-IO). At present, the internal fallbacks provided by Abinit do not support netcdf4 so you have to link against an external netcdf library that supports hdf5+MPI-IO and is compatible with the mpif90 used to compile Abinit. See ~abinit/doc/build/config-examples/ubu_gnu_4.9_mpich.ac for a typical configuration file.

References:





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iprcfc
Mnemonics: Integer for PReConditioner of Force Constants
Characteristic: DEVELOP
Variable type: integer
Default is 0

Used when iscf>0, to define the SCF preconditioning scheme. Potential-based preconditioning schemes for the SCF loop are still under development.
The present parameter (force constant part) describes the way a change of force is derived from a change of atomic position.
Supported values :

No meaning for RF calculations.





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irandom
Mnemonics: Integer for the choice of the RANDOM number generator
Characteristic: DEVELOP
Variable type: integer
Default is 3

For the time being, only used when imgmov=9 (Langevin Path-Integral Molecular Dynamics).
irandom defines the random number generator.

Supported values :

irandom=3 is strongly advised when performing Molecular Dynamics restarts (avoids bias).





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irdvdw
Mnemonics: Integer that governs the ReaDing of _VDW files
Characteristic: DEVELOP
Variable type: integer
Default is 0

Used when vdw_xc>0, to read previously calculated vdW-DF variables.
Supported values:





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irdwfkfine
Mnemonics: Integer that governs the ReaDing of the fine grid _WFK files
Characteristic:
Variable type: integer
Default is 0

Indicates eventual starting wavefunctions. As alternative, one can use the input variables getwfkfine.

Ground-state calculation :

Response-function calculation : Bethe-Salpeter calculation : This variable is experimental. In development.




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isecur
Mnemonics: Integer for level of SECURity choice
Characteristic: DEVELOP
Variable type: integer
Default is 0

In the presently used algorithms, there is a compromise between speed and robustness, that can be tuned by using isecur.
If isecur =0, an extrapolation of out-of-line data is allowed, and might save one non-SCF calculation every two line minimisation when some stability conditions are fulfilled (since there are 2 non-SCF calculations per line minimisation, 1 out of 4 is saved)
Using isecur=1 or higher integers will raise gradually the threshold to make extrapolation.
Using isecur=-2 will allow to save 2 non-SCF calculations every three line minimisation, but this can make the algorithm unstable. Lower values of isecur allows for more (tentative) savings. In any case, there must be one non-SCF computation per line minimisation.
No meaning for RF calculations yet.





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istatr
Mnemonics: Integer for STATus file SHiFT
Characteristic: DEVELOP, NO_MULTI
Variable type: integer
Default is 0 (Comment: Values lower than 10 may not work on some machines.)

Govern the rate of output of the status file. This status file is written when the number of the call to the status subroutine is equal to ' istatshft ' modulo 'istatr', so that it is written once every 'istatr' call. When 'istatr'=0, there is no writing of a status file (which is the default).





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istatshft
Mnemonics: Integer for STATus file SHiFT
Characteristic: DEVELOP, NO_MULTI
Variable type: integer
Default is 1

Govern the rate of output of the status file. This status file is written when the number of the call to the status subroutine is equal to 'istatshft' modulo ' istatr ', so that it is written once every ' istatr ' call. There is also a writing for each of the 5 first calls, and the 10th call.





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istwfk
Mnemonics: Integer for choice of STorage of WaveFunction at each k point
Characteristic:
Variable type: integer(nkpt)
Default is *0 (Comment: For RF calculations, the Default is not used : istwfk is forced to be 1 deep inside the code, for all k points. For spin-orbit calculations (nspinor=2), istwfk is also forced to be 1, for all k points.)

Control the way the wavefunction for each k-point is stored inside ABINIT, in reciprocal space.
For the GS calculations, in the "cg" array containing the wavefunction coefficients, there is for each k-point and each band, a segment cg(1:2,1:npw). The 'full' number of plane wave is determined by ecut. However, if the k-point coordinates are build only from zeroes and halves (see list below), the use of time-reversal symmetry (that connects coefficients) has been implemented, in order to use real-to-complex FFTs (see fftalg), and to treat explicitly only half of the number of plane waves (this being used as 'npw').
For the RF calculations, there is not only the "cg" array, but also the "cgq" and "cg1" arrays. For the time-reversal symmetry to decrease the number of plane waves of these arrays, the q vector MUST be (0 0 0). Then, for each k point, the same rule as for the RF can be applied.
WARNING (991018) : for the time being, the time-reversal symmetry cannot be used in the RF calculations.





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lotf_classic
Mnemonics: LOTF classic model for Glue model
Characteristic: DEVELOP
Variable type: integer
Default is 5

Glue model used in LOTF.
For the moment it is imposed to be 5.





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lotf_nitex
Mnemonics: LOTF number of iterations
Characteristic: DEVELOP
Variable type: integer
Default is 10

Set the number of Molecular Dynamics iterations which are computed by LOTF.





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lotf_nneigx
Mnemonics: LOTF max number of neighbours
Characteristic: DEVELOP
Variable type: integer
Default is 5

Set the max number of Neighbours used in the LOTF method.
For the moment it is imposed to be 40.





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lotf_version
Mnemonics: LOTF version of MD algorithm
Characteristic: DEVELOP
Variable type: integer
Default is 2

Set the MD algorithm in the LOTF method.
For the moment it is imposed to be 2.





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macro_uj
Mnemonics: Macro variable that activates the determination of the U and J parameter (for the PAW+U calculations)
Characteristic: DEVELOP
Variable type: integer
Default is 0

Sets proper input values for the determination of U and J i.e. for pawujat (first atom treated with PAW+U), irdwfk (=1), tolvrs (=10^(-8)), nstep (=255), diemix (=0.45), atvshift (pawujat) pawujv). Do not overwrite these variables manually unless you know what you do.

Determination of U and J can be done only if the symmetry of the atomic arrangement is reduced and the atom pawujat is not connected to any other atom by symmetry relations (either input reduced symmetries manually, define concerned atom as a separate atomic species or shift concerned atom from ideal position).





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maxnsym
Mnemonics: MAXimum Number of SYMetries
Characteristic: DEVELOP
Variable type: integer
Default is 384

Gives the maximum number of spatial symetries allowed in the memory.
The default value is sufficient for most applications; it has to be increase in the case of the use of a supercell (unit cell identically repeated).





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mem_test
Mnemonics: MEMory TEST
Characteristic: DEVELOP
Variable type: integer
Default is 1

This variable controls the memory test done in the memana routine. Possible values:





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mqgrid
Mnemonics: Maximum number of Q-space GRID points for pseudopotentials
Characteristic: DEVELOP
Variable type: integer
Default is 3001

Govern the size of the one-dimensional information related to pseudopotentials, in reciprocal space : potentials, or projector functions.





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nbdblock
Mnemonics: Number of BanDs in a BLOCK
Characteristic: DEVELOP
Variable type: integer
Default is 1

In case of non-standard, blocked algorithms for the optimization of the wavefunctions (that is, if wfoptalg=4):





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nc_xccc_gspace
Mnemonics: use XC Core-Correction in G-space
Characteristic: DEVELOP
Variable type: integer
Default is 0 if usepaw==0, 1 if usepaw==1, 0 otherwise. (Comment: 0 when usepaw=0, 1 when usepaw=1)

Historically, Abinit treats the model core charge used for the non-linear core correction in real space. Alternatively, it is possible to instruct the code to compute the core charge in G-space following the same approach used in the PAW code. The G-space formalism is more accurate than the interpolation in real space, especially when derivatives of the model core charge are needed, e.g. DFPT. Preliminary tests showed that the violation of the acoustic sum rule is reduced when nc_xccc_gspace==1 , especially for LDA. It is worth stressing, however, that nc_xccc_gspace==1 should be used only in conjunction with NC pseudos whose model core charge that decays quickly in G-space. Several NC pseudos available in the Abinit table are not optimized for the G-space formalism and users are strongly invited to perform convergence studies with respect to ecut before using this option.



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nctime
Mnemonics: NetCdf TIME between output of molecular dynamics informations
Characteristic: DEVELOP
Variable type: integer
Default is 0

When nctime is non-zero, the molecular dynamics information is output in NetCDF format, every nctime time step. Here is the content of an example file :

netcdf md32.outH_moldyn1 {
dimensions:
   time = UNLIMITED ; // (11 currently)
   DimTensor = 6 ;
   DimCoord = 3 ;
   NbAtoms = 32 ;
   DimVector = 3 ;
   DimScalar = 1 ;
variables:
   double E_pot(time) ;
      E_pot:units = "hartree" ;
   double E_kin(time) ;
      E_kin:units = "hartree" ;
   double Stress(time, DimTensor) ;
      Stress:units = "hartree/Bohr^3" ;
   double Position(time, DimCoord, NbAtoms) ;
      Position:units = "Bohr" ;
   double Celerity(time, DimCoord, NbAtoms) ;
      Celerity:units = "Bohr/(atomic time unit)" ;
   double PrimitiveVector1(DimVector) ;
   double PrimitiveVector2(DimVector) ;
   double PrimitiveVector3(DimVector) ;
   double Cell_Volume(DimScalar) ;
      Cell_Volume:units = "Bohr^3" ;
}
 





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nloc_alg
Mnemonics: Non LOCal ALGorithm
Characteristic: DEVELOP
Variable type: integer
Default is 4

Allows to choose the algorithm for non-local operator application. On super-scalar architectures, the default nloc_alg=4 is the best.
More detailed explanations:

- nloc_alg=2 : Should be efficient on vector machines. It is indeed the fastest algorithm for the NEC, but actual tests on Fujitsu machine did not gave better performances than the other options.
- nloc_alg=3 : same as nloc_alg==2, but the loop order is inverted.
- nloc_alg=4 : same as nloc_alg==3, but maximal use of registers has been coded. This should be especially efficient on scalar and super-scalar machines. This has been confirmed by tests.
Note: internally, nloc_alg is stored in nloalg(1) . See also nloc_mem for the tuning of the memory used in the non-local operator application.





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nloc_mem
Mnemonics: Non LOCal MEMOry
Characteristic: DEVELOP
Variable type: integer
Default is 2 if usepaw==1, 1 otherwise.

Controls the memory use for the application of the non-local operator.
More detailed explanations:

- nloc_mem==1 : (k+G) vectors are not precomputed, in order to save memory space.
- nloc_mem==2 : (k+G) vectors are precomputed, once per k-point.
- nloc_mem==-1 or -2 : Negative values of nloc_mem correspond positive ones, where the phase precomputation has been suppressed, in order to save memory space, as an array double precision :: ph3d(2,npw,natom) is saved (typically half the space needed for the wavefunctions at 1 k point - this corresponds to the silicon case). However, the computation of phases inside nonlop is somehow time-consuming.

Note: internally, sign(nloc_mem) is stored in nloalg(2) and abs(nloc_mem)-1 is stored in nloalg(3) . See also nloc_alg for the algorithm for the non-local operator application.





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nnsclo
Mnemonics: Number of Non-Self Consistent LOops
Characteristic: DEVELOP
Variable type: integer
Default is 0

Gives the maximum number of non-self-consistent loops of nline line minimisations, in the SCF case (when iscf >0). In the case iscf <=0 , the number of non-self-consistent loops is determined by nstep.
The Default value of 0 -- for standard plane-wave calculations -- corresponds to make the two first fixed potential determinations of wavefunctions have 2 non-self consistent loops, and the next ones to have only 1 non-self consistent loop.
The Default value of 0 -- for wavelets calculations (usewvl=1) -- corresponds to make 2 steps with 3 non-self consistent loops , 2 steps with 2 non-self consistent loops, then the next ones with 1 non-self consistent loop.





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nnsclohf
Mnemonics: Number of Non-Self Consistent LOops for Fock exact exchange
Characteristic: DEVELOP
Variable type: integer
Default is 1 if usefock==1, 0 otherwise.

Gives the maximum number of loops with non-self-consistent occupied states used to calculate Fock exact exchange, in the SCF case.
The Default value is 0 when usefock = 0. Default value is 1 when usefock = 1 and correspond to update occupied wavefunctions at each self-consistent loop.





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normpawu
Mnemonics: NORMalize atomic PAW+U projector
Characteristic: DEVELOP
Variable type: integer(ntypat)
Default is 0

Defines whether the atomic wave function (used as projectors in PAW+U) should be renormalized to 1 within PAW sphere.





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npulayit
Mnemonics: Number of PULAY ITerations for SC mixing
Characteristic: DEVELOP
Variable type: integer
Default is 7

Only relevant if iscf in [7,17]

Gives the number of previous iterations involved in Pulay mixing (mixing during electronic SC iterations).





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nscforder
Mnemonics: SCaling Function ORDER
Characteristic:
Variable type: integer
Default is 16

This variable controls the order of used scaling functions when the Hartree potential is computed using the Poisson solver (see icoulomb imput variable). This variable is of seldom use since the default value is large enough. Nonetheless, possible values are 8, 14, 16, 20, 24, 30, 40, 50, 60, 100. Values greater than 20 are included in ABINIT for test purposes only.





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optforces
Mnemonics: OPTions for the calculation of FORCES
Characteristic: DEVELOP
Variable type: integer
Default is 1 if toldff or tolrff != 0, 2 otherwise.

Allows to choose options for the calculation of forces.





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optnlxccc
Mnemonics: OPTion for the calculation of Non-Linear eXchange-Correlation Core Correction
Characteristic: DEVELOP
Variable type: integer
Default is 1

Allows to choose options for the calculation of non-linear XC correction. At present, only relevant for the FHI type of pseudopotentials, with pspcod=6 .





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ortalg
Mnemonics: ORThogonalisation ALGorithm
Characteristic: DEVELOP
Variable type: integer
Default is -2 if wfoptalg >= 10 , 2 otherwise.

Allows to choose the algorithm for orthogonalisation.
Positive or zero values make two projections per line minimisation, one before the preconditioning, one after. This is the clean application of the band-by-band CG gradient for finding eigenfunctions.
Negative values make only one projection per line minimisation.
The orthogonalisation step is twice faster, but the convergence is less good. This actually calls to a better understanding of this effect.
ortalg=0, 1 or -1 is the conventional coding.
ortalg=2 or -2 try to make better use of existing registers on the particular machine one is running.
More demanding use of registers is provided by ortalg=3 or -3, and so on.
The maximal value is presently 4 and -4.
Tests have shown that ortalg=2 or -2 is suitable for use on the available platforms.





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papiopt
Mnemonics: PAPI OPTion
Characteristic:
Variable type: integer
Default is 0

PAPI aims to provide the tool designer and application engineer with a consistent interface and methodology for use of the performance counter hardware found in most major microprocessors. PAPI enables software engineers to see, in near real time, the relation between software performance and processor events.
This option can be used only when ABINIT has been compiled with the --enable-papi configure option.
If papiopt=1, then PAPI counters are used instead of the usual time() routine. All the timing output of ABINIT is then done with PAPI values. The measurements are more accurate and give also access to the flops of the calculation.





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pawprt_b
Mnemonics: PAW print band
Characteristic: DEVELOP
Variable type: integer
Default is 0

Forces the output of the all-electron wavefunction for only a single band. To be used in conjuction with:
pawprtwf=1
and pawprt_k. The indexing of the bands start with one for the lowest occupied band and goes up from there.





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pawprt_k
Mnemonics: PAW print k-point
Characteristic: DEVELOP
Variable type: integer
Default is 0

Forces the output of the all-electron wavefunction for only a single k-point. To be used in conjuction with:
pawprtwf=1
and pawprt_b. The indexing follows the order in ouptput of the internal variable kpt in the beginning of the run.





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pawujat
Mnemonics: PAW+macro_UJ, ATom number
Characteristic: DEVELOP
Variable type: integer
Default is 1 (Comment: i.e. the first atom treated with PAW+U.)

Determines the atom for which U (or J) should be determined. See also macro_uj.





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pawujrad
Mnemonics: PAW+macro_UJ, sphere RADius
Characteristic: DEVELOP
Variable type: real
Default is 20 a.u.

The sphere radius serves to extrapolate the U value calculated at r_paw to a larger sphere radius. See also macro_uj. As most projector functions are localized within r_paw to ≈80%, 20 a.u. contains ≈100% of the wavefunction and corresponds to r_paw → ∞.





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pawujv
Mnemonics: PAW+macro_UJ, potential shift (V)
Characteristic: DEVELOP
Variable type: real
Default is 0.1 eV

Amplitude of the potential shift for the determination of U (or J). See also macro_uj.





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plowan_bandf
Mnemonics: Projected Local Orbital WANnier functions Initial BAND
Characteristic: DEVELOP
Variable type: integer
Default is 0


Gives the upper band to include in the calculation of Wannier functions





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plowan_bandi
Mnemonics: Projected Local Orbital WANnier functions Initial BAND
Characteristic: DEVELOP
Variable type: integer
Default is 0


Gives the lower band to include in the calculation of Wannier functions





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plowan_compute
Mnemonics: Projected Local Orbital WANnier functions COMPUTATION
Characteristic: DEVELOP
Variable type: integer
Default is 0


Activate computation of Projected Local Orbital Wannier functions (PLO Wannier) and corresponding band structure. Variables plowan_bandi, plowan_bandf, plowan_natom, plowan_nbl, plowan_iatom, plowan_lcalc, plowan_projcalc are mandatory to precise the nature of the projections.

Other related variables are plowan_realspace, plowan_nt, plowan_it. The implementation is not symetrized over k-point and not parallelized. (The calculation of projections is detailed in Phys. Rev. B 77, 205112, (2008) )





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plowan_iatom
Mnemonics: Projected Local Orbital WANnier functions, ATOM Index
Characteristic: DEVELOP
Variable type: integer
Default is 0


Gives the indices of the plowan_natom atoms on which the projections will be done.





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plowan_it
Mnemonics: Projected Local Orbital WANnier functions, Index of Translation.
Characteristic: DEVELOP
Variable type: integer(3,plowan_nt)
Default is 0


Requires plowan_realspace to be greater than 0 and plowan_nt to be greater than 0. Precise a given set of selected real space translation by using the real space vectors basis. These atoms are used to define Wannier functions in real space. These real space Wannier functions are used as a basis to compute the Hamiltonian.





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plowan_lcalc
Mnemonics: Projected Local Orbital WANnier functions, L values to use for CALCulation
Characteristic: DEVELOP
Variable type: integer(sum(plowan_nbl))
Default is -1


Gives the plowan_nbl values of angular momenta for each atom, in the order of the atoms as given in plowan_iatom.





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plowan_natom
Mnemonics: Projected Local Orbital WANnier functions, Number of ATOMs
Characteristic: DEVELOP
Variable type: integer
Default is 0


Gives the number of atoms on which the projection will be done





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plowan_nbl
Mnemonics: Projected Local Orbital WANnier functions, NumBer of L values
Characteristic: DEVELOP
Variable type: integer(plowan_natom)
Default is 0


Gives the total number of angular momenta (over all atoms) to compute the projections.





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plowan_nt
Mnemonics: Projected Local Orbital WANnier functions, Number of Translation on which the real space values of energy are computed
Characteristic: DEVELOP
Variable type: integer
Default is 0


Requires plowan_realspace to be greater than 0. Gives a number of selected atoms. These atoms are used to define Wannier functions in real space. These real space Wannier functions are used as a basis to compute the Hamiltonian.





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plowan_projcalc
Mnemonics: Projected Local Orbital WANnier functions, PROJectors values to use for CALCulation
Characteristic: DEVELOP
Variable type: integer(sum(plowan_nbl))
Default is -1


Gives the plowan_nbl values of projectors for each atom, in the order of the atoms as given in plowan_iatom. The index i for the projectors refers to the ith number on line orbitals of the PAW atomic data file.





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plowan_realspace
Mnemonics: Projected Local Orbital WANnier functions, activate REAL SPACE calculation.
Characteristic: DEVELOP
Variable type: integer
Default is 0

Can take the following values:





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prepscphon
Mnemonics: PREPare Self-Consistent PHONon calculation
Characteristic: DEVELOP
Variable type: integer
Default is 0

Print PCINFO, PHFREQ, and PHVEC files, for use with self-consistent phonon runs, after a perturbation calculation. Only prints out files for the present q-point, and there is presently no tool to symmetrize or merge these files, so use anaddb instead (with prtscphon input variable). The abinit input variable is destined to someday bypass the use of anaddb for scphon calculations.





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prtbltztrp
Mnemonics: PRinT output for BoLTZTRaP code
Characteristic: DEVELOP
Variable type: integer
Default is 0

Print out geometry (_BLZTRP_GEOM) and eigenenergy (_BLZTRP_EIGEN) files for the BoltzTraP code by Georg Madsen.





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prtcif
Mnemonics: PRinT Crystallographic Information File
Characteristic: DEVELOP
Variable type: integer
Default is 0

If set to 1, a CIF file is output with the crystallographic data for the present run (cell size shape and atomic positions).





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prtdipole
Mnemonics: PRinT DIPOLE
Characteristic: DEVELOP
Variable type: integer
Default is 0

Print out dipole of unit cell, calculated in real space for the primitive cell only. Under development.





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prtnest
Mnemonics: PRinT NESTing function
Characteristic: DEVELOP
Variable type: integer
Default is 0

If set to 1, the nesting function for the k-point grid is printed. For the moment the path in q space for the nesting function is fixed, but will become an input as well.





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prtposcar
Mnemonics: PRinT POSCAR file
Characteristic: DEVELOP
Variable type: integer
Default is 0

Print out VASP-style POSCAR and FORCES files, for use with PHON or frophon codes for frozen phonon calculations. See the associated script in ~abinit/extras/post_processing/phondisp2abi.py for further details on interfacing with PHON, PHONOPY, etc...





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prtvdw
Mnemonics: PRinT Van Der Waals file
Characteristic: DEVELOP
Variable type: integer
Default is 0

Print out a NetCDF file containing a vdW-DF kernel.



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recefermi
Mnemonics: RECursion - initial guess of the FERMI Energy
Characteristic: DEVELOP
Variable type: real
Default is 0

Used in Recursion method (tfkinfunc=2). In the first SCF calculation it fixes the initial guess for the Fermi energy.





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recgratio
Mnemonics: RECursion - Grid Ratio
Characteristic: DEVELOP
Variable type: integer
Default is 1

Used in Recursion method (tfkinfunc=2). It represents the ratio of the two grid step: recgratio=fine_step/coarse_step and it is bigger or equal than 1. It introduces a double-grid system which permits to compute the electronic density on a coarse grid, using a fine grid (defined by ngfft) in the discretisation of the green kernel (see recptrott). Successively the density and the recursion coefficients are interpolated on the fine grid by FFT interpolation. Note that ngfft/recgratio=number of points of the coarse grid has to be compatible with the parallelization parameters.





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recnpath
Mnemonics: RECursion - Number of point for PATH integral calculations
Characteristic: DEVELOP
Variable type: integer
Default is 500

Used in Recursion method (tfkinfunc=2). Determine the number of discretisation points to compute some path integral in the recursion method ; those path integrals are used to compute the entropy and the eigenvalues energy. during the latest SFC cycles.





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recnrec
Mnemonics: RECursion - Number of RECursions
Characteristic: DEVELOP
Variable type: integer
Default is 10

Used in Recursion method (tfkinfunc=2). Determine the maximum order of recursion, that is the dimension of the krylov space we use to compute density. If the precision set by rectolden is reached before that order, the recursion method automatically stops.





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recptrott
Mnemonics: RECursion - TROTTer P parameter
Characteristic: DEVELOP
Variable type: integer
Default is 0

Used in Recursion method (tfkinfunc=2). Determine the trotter parameter used to compute the exponential of the hamiltonian in the recursion method: exp(-beta*(-Delta + V)) ~ (exp(-beta/(4*recptrott) V) exp(-beta/(4*recptrott) Delta) exp(-beta/(4*recptrott) V))^(2*recptrott). If set to 0, we use recptrott = 1/2 in the above formula. Increasing recptrott improve the accuracy of the trotter formula, but increase the dicretisation error: it may be necessary to increase ngfft. The discretisation error is essentially the discretisation error of the green kernel exp((recptrott/beta*|r|^2)) on the ngfft grid.





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recrcut
Mnemonics: RECursion - CUTing Radius
Characteristic: DEVELOP
Variable type: integer
Default is 0

Used in Recursion method (tfkinfunc=2). Used to improve the computational time in the case of the recursion method in a large cell: the density at a point will be computed with taking account only of a sphere of radius recrcut.





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rectesteg
Mnemonics: RECursion - TEST on Electron Gas
Characteristic: DEVELOP
Variable type: integer
Default is 0

Used in Recursion method (tfkinfunc=2). It is used to test an electron gas by putting the ion potential equal to zero.





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rectolden
Mnemonics: RECursion - TOLerance on the difference of electronic DENsity
Characteristic: DEVELOP
Variable type: real
Default is 0.0 (Comment: Default value to be changed.)

Used in Recursion method (tfkinfunc=2). Sets a tolerance for differences of electronic density that, reached TWICE successively, will cause one SCF cycle to stop. That electronic density difference is computed in the infinity norm (that is, it is computed point-by-point, and then the maximum difference is computed).





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symmorphi
Mnemonics: SYMMORPHIc symmetry operations
Characteristic: DEVELOP, GW
Variable type: integer
Default is 1

With symmorphi=1, symmetry operations with a non-symmorphic vector are allowed. With symmorphi=0, they are not allowed. In the latter case, if the symmetry operations are specified in the input file, the code will stop and print an error message if a non-symmorphic vector is encountered. By contrast, if the symmetry operations are to be determined automatically (if nsym=0), then the set of symmetries will not include the non-symmorphic operations.

Note : this feature exist because in a previous status of the GW calculations, non-symmorphic symmetry operations could not be exploited. Thus, the k points were restricted to the IBZ. In order to prepare GW calculations, and to perform GW calculations, symmorphi=0 was to be used, together with nsym=0.





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tfkinfunc
Mnemonics: Thomas-Fermi KINetic energy FUNCtional
Characteristic: DEVELOP
Variable type: integer
Default is 0





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tfw_toldfe
Mnemonics: Thomas-Fermi-Weizsacker: TOLerance on the DiFference of total Energy, for initialization steps
Characteristic: ENERGY
Variable type: real
Default is 1.0E-6 or toldfe is present

Only relevant if tfkinfunc=11

This input variable has the same definition as toldfe and is only relevant when tfkinfunc=11.
It sets a tolerance for absolute differences of total energy that, reached TWICE successively, will cause the initialization steps (without gradient correction) to stop and the gradient correction to be added.
Can be specified in Ha (the default), Ry, eV or Kelvin, since it has the 'ENERGY' characteristics.




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tolrde
Mnemonics: TOLerance on the Relative Difference of Eigenenergies
Characteristic:
Variable type: real
Default is 0.005

Sets a tolerance for the ratio of differences of eigenenergies in the line minimisation conjugate-gradient algorithm. It compares the decrease of the eigenenergy due to the last line minimisation, with the one observed for the first line minimisation. When the ratio is lower than tolrde, the next line minimisations are skipped.
The number of line minimisations is limited by nline anyhow.
This stopping criterion is present for both GS and RF calculations. In RF calculations, tolrde is actually doubled before comparing with the above-mentioned ratio, for historical reasons.





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use_gemm_nonlop
Mnemonics: USE the GEMM routine for the application of the NON-Local OPerator
Characteristic: DEVELOP
Variable type: integer
Default is 0 (Comment: because it is not usually worth using it unless bandpp is large and it requires additional memory)

This keyword tells abinit to use a BLAS routine to speed up the computation of the non-local operator. This requires the precomputation of a large matrix, and has a significant memory overhead. In exchange, it provides improved performance when used on several bands at once (Chebyshev or LOBPCG algorithm with bandpp

The memory overhead is proportional to the number of atoms, the number of plane waves, and the number of projectors per atom. It can be mitigated by distributing the array with npfft

The performance depends crucially on having a good BLAS installed. Provided the BLAS supports OpenMP, this option also yields very good scaling for the nonlocal operator.





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use_nonscf_gkk
Mnemonics: USE NON-SCF calculation of GKK matrix elements (electron phonon)
Characteristic: DEVELOP
Variable type: integer
Default is 0 (Comment: Default is 0 for the moment. Do not use non-scf method.)

When this flag is activated during a phonon calculation with abinit, all of the perturbations are cycled through, but only the symmetry-irreducible ones are calculated self-consistently. For the others the perturbed density is rotated by the appropriate symop and the gkk matrix elements are calculated non-self-consistently. As they do not depend on the perturbed wave functions, they are correct from the first iteration, and nstep is set to 1 for those perturbations. Note that the resulting 1DEN files are simply the rotate/symmetric ones and that the resulting 1WF files are garbage (completely unconverged) except the matrix elements in the header (equivalent to GKK files, but please use the latter much smaller files for el-ph calculations). The new default behavior with use_nonscf_gkk = 1 should be transparent for the user, with the same output files but a much quicker execution.

Caveat: Note that very tight convergence of ground state and phonon calculations is necessary to get good GKK matrix elements! tolwfr = 1.e-24 or so is recommended everywhere. There may be problems using use_nonscf_gkk = 1 with non-symmorphic symmetries - please check (at least) that lifetimes for phonons go to 0 for acoustic modes at Gamma.





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usedmft
Mnemonics: USE Dynamical Mean Field Theory
Characteristic: DEVELOP
Variable type: integer
Default is 0

If set to 1, enable the use of DFT+DMFT, see in particular the important variables dmft_solv, dmftbandi, dmftbandf, dmft_nwli, dmft_nwlo, dmft_tollc, dmft_tolfreq, and dmft_iter.

The current implementation uses Wannier functions obtained from projected local orbitals as correlated orbitals (see dmftbandi and dmftbandf input variables to define them).

The Green functions are computed on a mesh of linear Matsubara frequencies. However, most of the code uses logarithmic Matsubara grid to lower the computational cost. Both dmft_nwli and dmft_nwlo are thus convergence parameters.

DMFT is currently available for collinear (nspinor=1) polarized or unpolarized calculations (nspden=nsppol=2 or nspden=nsppol=1) and for non collinear calculations (nspinor=2,nspden=4,nsppol=1). However it is not yet available for collinear antiferromagnetic calculations (nspden=2,nsppol=1) and non collinear non magnetic calculations (nspden=1, nsppol=1,nspinor=2). CTQMC calculations (dmft_solv=5) are not yet possible if nspinor=2.

Only static calculations without relaxation or dynamics are possible (forces and stress are not computed in the scheme: so the computed values should NOT be trusted).

When correlated density matrices are diagonal, all values of upawu and jpawu are possible. If the correlated density matrices are non diagonal, only jpawu = 0 is implemented.

Relevant direct output quantities from converged DMFT calculations are total energy and occupation of correlated orbitals. For Hubbard I calculation (dmft_solv=2), total and partial spectral functions can be obtained with prtdos=1 and can be found in files OUTSpFunc* (where OUT is the root for output files). For CTQMC calculations (dmft_solv=5), imaginary time impurity Green function are output of the calculations and can be used to produce spectral function using an external Maximum Entropy Code.

A typical DFT+DMFT calculation involves two runs. First, a DFT calculation is fully converged (even unoccupied wavefunctions have to be converged). Then, the DFT+DMFT calculation is started using DFT wavefunctions or density files. As DFT+DMFT calculations (with CTQMC) are computationnally expensive, it is convenient to use prtden=-1, to write DEN file at each DFT iteration, in order to be able to restart the calculation easily.

For details of the implementation see, B. Amadon, F. Lechermann, A. Georges, F. Jollet, T. O. Wehling, and A. I. Lichtenstein, Phys. Rev. B 77(20), (2008) , for Wannier functions and B. Amadon, J. Phys.: Condens. Matter 24 075604 (2012) (doi:10.1088/0953-8984/24/7/075604), for self-consistency and Hubbard I implementation. If usedmft=1 and nbandkss/=0, then, the DFT+DMFT calculation is not done and only projections are computed at the end of the calculation. They can be used by an external code or used to compute the screened interaction (see variable ucrpa).





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useria
Mnemonics: USER Integer variable A
Characteristic:
Variable type: integer
Default is 0

These are user-definable integers which the user may input and then utilize in subroutines of his/her own design. They are not used in the official versions of the ABINIT code, and should ease independent developments (hopefully integrated in the official version afterwards).
Internally, they are available in the dtset structured datatype, e.g. dtset%useria .





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userib
Mnemonics: USER Integer variable B
Characteristic:
Variable type: integer
Default is 0

These are user-definable integers which the user may input and then utilize in subroutines of his/her own design. They are not used in the official versions of the ABINIT code, and should ease independent developments (hopefully integrated in the official version afterwards).
Internally, they are available in the dtset structured datatype, e.g. dtset%useria .





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useric
Mnemonics: USER Integer variable C
Characteristic:
Variable type: integer
Default is 0

These are user-definable integers which the user may input and then utilize in subroutines of his/her own design. They are not used in the official versions of the ABINIT code, and should ease independent developments (hopefully integrated in the official version afterwards).
Internally, they are available in the dtset structured datatype, e.g. dtset%useria .





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userid
Mnemonics: USER Integer variable D
Characteristic:
Variable type: integer
Default is 0

These are user-definable integers which the user may input and then utilize in subroutines of his/her own design. They are not used in the official versions of the ABINIT code, and should ease independent developments (hopefully integrated in the official version afterwards).
Internally, they are available in the dtset structured datatype, e.g. dtset%useria .





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userie
Mnemonics: USER Integer variable E
Characteristic:
Variable type: integer
Default is 0

These are user-definable integers which the user may input and then utilize in subroutines of his/her own design. They are not used in the official versions of the ABINIT code, and should ease independent developments (hopefully integrated in the official version afterwards).
Internally, they are available in the dtset structured datatype, e.g. dtset%useria .





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userra
Mnemonics: USER Real variable A
Characteristic:
Variable type: real
Default is 0.0

These are user-definable with the same purpose as useria and cie.





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userrb
Mnemonics: USER Real variable B
Characteristic:
Variable type: real
Default is 0.0

These are user-definable with the same purpose as useria and cie.





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userrc
Mnemonics: USER Real variable C
Characteristic:
Variable type: real
Default is 0.0

These are user-definable with the same purpose as useria and cie.





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userrd
Mnemonics: USER Real variable D
Characteristic:
Variable type: real
Default is 0.0

These are user-definable with the same purpose as useria and cie.





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userre
Mnemonics: USER Real variable E
Characteristic:
Variable type: real
Default is 0.0

These are user-definable with the same purpose as useria and cie.





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useylm
Mnemonics: USE YLM (the spherical harmonics)
Characteristic: DEVELOP
Variable type: integer
Default is 1 if usepaw==1, 1 if tfkinfunc==1, 0 otherwise.

When this flag is activated, the non-local operator is applied using an algorithm based on spherical harmonics. Non-local projectors are used with their usual form:



When useylm=0, the sum over Y_lm can be reduced to a Legendre polynomial form.





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vdw_df_acutmin
Mnemonics: vdW-DF MINimum Angular CUT-off
Characteristic: DEVELOP
Variable type: real
Default is 10

Only relevant if vdw_xc>0

Used when vdw_xc>0, to build angular meshes for the vdW-DF kernel.




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vdw_df_aratio
Mnemonics: vdW-DF RATIO between the highest and lowest Angle.
Characteristic: DEVELOP
Variable type: real
Default is 30

Only relevant if vdw_xc>0

Used when vdw_xc>0, to build angular meshes for the vdW-DF kernel.




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vdw_df_damax
Mnemonics: vdW-DF MAXimum Angular Delta
Characteristic: DEVELOP
Variable type: real
Default is 0.5

Only relevant if vdw_xc>0

Used when vdw_xc>0, to build angular meshes for the vdW-DF kernel.




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vdw_df_damin
Mnemonics: vdW-DF MINimum Angular Delta
Characteristic: DEVELOP
Variable type: real
Default is 0.01

Only relevant if vdw_xc>0

Used when vdw_xc>0, to build angular meshes for the vdW-DF kernel.




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vdw_df_dcut
Mnemonics: vdW-DF D-mesh CUT-off
Characteristic: DEVELOP
Variable type: real
Default is 30

Only relevant if vdw_xc>0

Used when vdw_xc>0, to build the vdW-DF kernel.




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vdw_df_dratio
Mnemonics: vdW-DF RATIO between the highest and lowest D.
Characteristic: DEVELOP
Variable type: real
Default is 20

Only relevant if vdw_xc>0

Used when vdw_xc>0, to build the vdW-DF kernel.




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vdw_df_dsoft
Mnemonics: vdW-DF SOFTening distance.
Characteristic: DEVELOP
Variable type: real
Default is 1.0

Only relevant if vdw_xc>0

Used when vdw_xc>0, to build the vdW-DF kernel.




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vdw_df_gcut
Mnemonics: vdW-DF K-space CUT-off
Characteristic: DEVELOP
Variable type: real
Default is 5

Only relevant if vdw_xc>0

Used when vdw_xc>0, to filter the vdW-DF kernel in reciprocal space.




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vdw_df_ndpts
Mnemonics: vdW-DF Number of D-mesh PoinTS
Characteristic: DEVELOP
Variable type: integer
Default is 20

Only relevant if vdw_xc>0

Used when vdw_xc>0, to build the vdW-DF kernel.




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vdw_df_ngpts
Mnemonics: vdW-DF Number of G-mesh PoinTS
Characteristic: DEVELOP
Variable type: integer
Default is -1

Only relevant if vdw_xc>0

Used when vdw_xc>0, to build the vdW-DF kernel.




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vdw_df_nqpts
Mnemonics: vdW-DF Number of Q-mesh PoinTS
Characteristic: DEVELOP
Variable type: integer
Default is 30

Only relevant if vdw_xc>0

Used when vdw_xc>0, to build the vdW-DF kernel.




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vdw_df_nrpts
Mnemonics: vdW-DF Number of R-PoinTS
Characteristic: DEVELOP
Variable type: integer
Default is 2048

Only relevant if vdw_xc>0

Used when vdw_xc>0, to define the sampling of the vdW-DF-kernel in real-space.




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vdw_df_nsmooth
Mnemonics: vdW-DF Number of SMOOTHening iterations
Characteristic: DEVELOP
Variable type: integer
Default is 12

Only relevant if vdw_xc>0

Used when vdw_xc>0, to exponentially smoothen q near q0.




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vdw_df_phisoft
Mnemonics: vdW-DF SOFTening PHI value.
Characteristic: DEVELOP
Variable type: real
Default is -1.0

Only relevant if vdw_xc>0

Used when vdw_xc>0, to build the vdW-DF kernel.




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vdw_df_qcut
Mnemonics: vdW-DF Q-mesh CUT-off
Characteristic: DEVELOP
Variable type: real
Default is 5

Only relevant if vdw_xc>0

Used when vdw_xc>0, to build the vdW-DF kernel.




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vdw_df_qratio
Mnemonics: vdW-DF RATIO between highest and lowest Q
Characteristic: DEVELOP
Variable type: real
Default is 20

Only relevant if vdw_xc>0

Used when vdw_xc>0, .




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vdw_df_rcut
Mnemonics: vdW-DF Real-space CUT-off
Characteristic: DEVELOP
Variable type: real
Default is 100

Only relevant if vdw_xc>0

Used when vdw_xc>0, to define the vdW-DF kernel cut-off radius.




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vdw_df_rsoft
Mnemonics: vdW-DF SOFTening radius.
Characteristic: DEVELOP
Variable type: real
Default is 0.0

Only relevant if vdw_xc>0

Used when vdw_xc>0, to build the vdW-DF kernel.




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vdw_df_threshold
Mnemonics: vdW-DF energy calculation threshold
Characteristic: DEVELOP
Variable type: real
Default is 0.01

Only relevant if vdw_xc>0

Sets a threshold for the energy gradient that, when reached, will cause the vdW-DF interactions to be calculated.
Adjust it to a big value (e.g. 1e12) to enable it all along the SCF calculation. Too small values, as well as negative values, will result in the vdW-DF energy contributions never being calculated.





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vdw_df_tolerance
Mnemonics: vdW-DF global TOLERANCE.
Characteristic: DEVELOP
Variable type: real
Default is 1e-13

Only relevant if vdw_xc>0

Used when vdw_xc>0, to build the vdW-DF kernel.




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vdw_df_tweaks
Mnemonics: vdW-DF tweaks.
Characteristic: DEVELOP
Variable type: integer
Default is 0

Only relevant if vdw_xc>0

Used when vdw_xc>0, to build the vdW-DF kernel.
IMPORTANT NOTE: modifying this variable will likely transform the calculated energies and their gradients into garbage. You have been warned!




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vdw_df_zab
Mnemonics: vdW-DF Zab parameter
Characteristic: DEVELOP
Variable type: real
Default is -0.8491

Only relevant if vdw_xc>0

Used when vdw_xc>0, as introduced in doi:10.1103/PhysRevLett.92.246401 .




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vdw_nfrag
Mnemonics: van der Waals Number of interacting FRAGments
Characteristic: DEVELOP
Variable type: integer
Default is 1

Only relevant if vdw_xc in [10,11]

The absolute value of vdw_nfrag is the number of vdW interacting fragments in the unit cell. As wannierization takes place in reciprocal space, the MLWF center positions could be translated by some lattice vector from the cell where atoms are placed. If vdw_nfrag >= 1 then MLWFs are translated to the original unit cell, otherwise the program will keep the positions obtained by Wannier90. The later is usually correct if some atoms are located at the corners or at limiting faces of the unit cell.





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vdw_supercell
Mnemonics: Van Der Waals correction from Wannier functions in SUPERCELL
Characteristic: DEVELOP
Variable type: integer(3)
Default is [0, 0, 0]

Only relevant if vdw_xc in [10,11]

Set of dimensionless positive numbers which define the maximum multiples of the primitive translations (rprimd) in the supercell construction. Each component of vdw_supercell indicates the maximum number of cells along both positive or negative directions of the corresponding primitive vector i.e. the components of rprimd. In the case of layered systems for which vdW interactions occur between layers made of tightly bound atoms, the evaluation of vdW corrections coming from MLWFs in the same layer (fragment) must be avoided. Both a negative or null value for one component of vdw_supercell will indicate that the corresponding direction is normal to the layers.





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vdw_tol
Mnemonics: van der Waals TOLerance
Characteristic: DEVELOP
Variable type: real
Default is 1e-10

Only relevant if vdw_xc==5

The DFT-D methods (S. Grimme approach) dispersion potentials, vdw_xc==5 or 6 or 7, include a pair potential. The number of pairs of atoms contributing to the potential is necessarily limited. To be included in the potential a pair of atom must have contribution to the energy larger than vdw_tol.





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vdw_tol_3bt
Mnemonics: van der Waals TOLerance for 3-Body Term
Characteristic: DEVELOP
Variable type: real
Default is -1 (Comment: Do include the 3-body term in the correction)

Only relevant if vdw_xc == 6

Control the computation of the 3-body correction inside DFT-D3 dispersion correction (Grimme approach) to the total energy:
-If vdw_tol_3bt<0, no 3-body correction.
-If vdw_tol_3bt>0, the 3-body term is included with a tolerance = vdw_tol_3bt

DFT-D3 as proposed by S. Grimme adds two contributions to the total energy in order to take into account of the dispersion:

The last term has been predicted to have an important effect for large molecules (see for e.g. Grimme S., J. Chem. Phys. 132, 154104 (2010) ). It is however quite costly in computational time for periodic systems and seems to lead to an overestimation of lattice parameters for weakly bound systems (see for e.g. Reckien W., J. Chem. Phys. 132, 154104(2010) ). Still, its contribution to energy, to forces and to stress is available (not planned for elastic constants, dynamical matrix and internal strains)




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vdw_typfrag
Mnemonics: van der Waals TYPe of FRAGment
Characteristic: DEVELOP
Variable type: integer(natom)
Default is 1*natom

Only relevant if vdw_xc in [10,11]

This array defines the interacting fragments by assigning to each atom an integer index from 1 to vdw_nfrag . The ordering of vdw_typfrag is the same as typat or xcart. Internally each MLWF is assigned to a given fragment by computing the distance to the atoms. MLWFs belong to the same fragment as their nearest atom. The resulting set of MLWFs in each interacting fragment can be found in the output file in xyz format for easy visualization.





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vdw_xc
Mnemonics: van der Waals eXchange-Correlation functional
Characteristic: DEVELOP
Variable type: integer
Default is 0

Selects a van-der-Waals density functional to apply the corresponding correction to the exchange-correlation energy. If set to zero, no correction will be applied.
Possible values are:

For vdw_xc=1 and vdw_xc=2, the implementation follows the strategy devised in the article of Román-Pérez and Soler (doi:10.1103/PhysRevLett.103.096102)





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wfoptalg
Mnemonics: WaveFunction OPTimisation ALGorithm
Characteristic: DEVELOP
Variable type: integer
Default is AUTO_FROM_PSP (Comment: 0 when usepaw=0 (norm-conserving pseudopotentials), 10 when usepaw=1 (PAW) ; 114 if paral_kgb=1.)

Allows one to choose the algorithm for the optimisation of the wavefunctions.
The different possibilities are :





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xc_denpos
Mnemonics: eXchange-Correlation - DENsity POSitivity value
Characteristic: DEVELOP
Variable type: real
Default is 1e-14

For the evaluation of the exchange-correlation functionals, the density cannot be negative, or even too small (e.g. the LDA exchange kernel behaves like the density at power -(2/3), and the density is used at the denominator of different factors in GGAs and metaGGAs. xc_denpos is the smallest value that the density can assume at the time of the evaluation of a XC functional, in ABINIT. When then computed density drops below xc_denpos before attacking the evaluation of the XC functional, then it will be (only for that purpose) replaced by xc_denpos. Note that the evaluation of the gradients or other quantities that are density-dependent is performed before this replacement.

It has been observed that the SCF cycle of the Tran-Blaha mGGA can be quite hard to make converge, for systems for which there is some vacuum. In this case, setting xc_denpos to 1.0e-7 ... 1.0e-6 has been seen to allow good convergence. Of course, this will affect the numerical results somehow, and one should play a bit with this value to avoid incorrect calculations.





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xc_tb09_c
Mnemonics: Value of the c parameter in the eXchange-Correlation TB09 functional
Characteristic:
Variable type: real
Default is 99.99

The modified Becke-Johnson exchange-correlation functional by Tran and Blaha (Phys. Rev. Lett. 102, 226401 (2009)) reads :

V_x(r) = c * V_x^{BR}(r) + (3*c - 2) * 1/pi * sqrt(5/12) * sqrt(2*kden(r)/den(r))

in which V_x^{BR}(r) is the Becke-Roussel potential.

In this equation the parameter c can be evaluated at each SCF step according to the following equation :

c = alpha + beta * sqrt(1/V_{cell} * \int_{V_{cell}} |grad(den(r))|/den(r) d3r)

The c parameter is evaluated thanks to the previous equation when xc_tb09_c is equal to the "magic" default value 99.99. The c parameter can also be fixed to some (property-optimized or material-optimized) value by using this variable.





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