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# 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.

The new user is advised to read first the new user's guide, before reading the present file. It will be easier to discover the present file with the help of the tutorial.

When the user is sufficiently familiarized with ABINIT, the reading of the ~abinit/doc/users/tuning file might be useful. For response-function calculations using abinit, please read the response function help file

### Content of the file : alphabetical list of developper variables.

A. accesswff
B. bandpp   builtintest
C.
D. densty   dmft_dc   dmft_iter   dmft_mxsf   dmft_nwli   dmft_nwlo   dmft_read_occnd   dmft_rslf   dmft_solv   dmft_tollc   dmftbandf   dmftbandi   dmftcheck
E. effmass   eshift   exchmix   exchn2n3d
F. fermie_nest   fftalg   fftcache   fft_opt_lob   freqsusin   freqsuslo
G. getgam_eig2nkq   gpu_linalg_limit
H.
I. idyson   ikhxc   intexact   intxc   iprcch   iprcfc   irandom   isecur   istatr   istatshft   istwfk
J.
K.
L. ldgapp
M. macro_uj   maxnsym   mqgrid
N. nbandsus   nbdblock   nctime   ndyson   nloalg   nnsclo   normpawu   noseft   noseinert   np_slk   npulayit   nscforder
O. optforces   optfreqsus   optnlxccc   ortalg
P. papiopt   pawprt_b   pawprt_k   pawujat   pawujrad   pawujv   prepscphon   prtbltztrp   prtcif   prtdipole   prtnest   prtposcar
Q.
R. recefermi   recgratio   recnpath   recnrec   recptrott   recrcut   rectesteg   rectolden
S. suskxcrs   symmorphi
T. tfkinfunc   tolrde
U. use_slk   useria, userib, useric, userid, userie   userra, userrb, userrc, userrd, userre   useylm
V. vdw_nfrag   vdw_tol   vdw_typfrag   vdw_supercell   vdw_xc
W. wfoptalg
X. xc_tb09_c
Y.
Z.

accesswff
Characteristic: DEVELOP
Variable type: integer parameter
Default is 0. However, if mpi_io is available, accesswff will be set to 1 for the datasets for which paral_kgb=1, while an explicit mention of accesswff in the input file will override this intermediate default.

Governs the method of access to the internal wavefunction files. Relevant only for the wavefunctions files for which the corresponding "mkmem"-type variable is zero, that is, for the wavefunctions that are not kept in core memory.

• 0 => Use standard Fortran IO routines
• 1 => Use MPI/IO routines
• 2 => Directly use NetCDF routines (this option is not available)
• 3 => Use ETSF_IO routines, creating NetCDF files according to the ETSF specification.

In case accesswff=1, note the following. MPI/IO routines might be much more efficient than usual Fortran IO routines in the case of a large number of processors, with a pool of disks attached globally to the processors, but not one disk attached to each processor. For a cluster of workstations, where each processor has his own temporaries, the use of accesswff=0 might be perfectly allright. This option is useful only if one is using the band-FFT parallelism. MPI/IO routines are available in the MPI-2 library, but usually not in the MPI-1 library. So, perhaps you cannot use accesswff=1.
In case accesswff=3, note that not only the wavefunctions will be written using the ETSF_IO routines, but also, the same input variable governs the writing of the density and potential, that can also be written using ETSF_IO routines. In order to use accesswff=3, you need to have the plug-in library ETSF_IO working (see the documentation of the build system). References :
• "Specification of an extensible and portable file format for electronic structure and crystallographic data", X. Gonze, C.-O. Almbladh, A. Cucca, D. Caliste, C. Freysoldt, M. Marques, V. Olevano, Y. Pouillon, M.J. Verstraete, Comput. Mat. Science 43, 1056 (2008)
• "Sharing electronic structure and crystallographic data with ETSF_IO", D. Caliste, Y. Pouillon, M.J. Verstraete, V. Olevano, X. Gonze, Comput. Physics Communications 179, 748 (2008)

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bandpp
Mnemonics: BAND Per Processor
Characteristic: DEVELOP
Variable type: integer parameter
Default is 1.

Control the size of the block in the LOBPCG algorithm. This keyword works only with paral_kgb=1 and has to be either 1 or a multiple of 2.

-- With npband=1:

• 1 => band-per-band algorithm
• n => The minimization is performed using nband/n blocks of n bands.
Note: nband/n has to be an integer.

-- With npband/=1:
Note: nband/(npband*n) has to be an integer.

By minimizing a larger number of bands together in LOBPCG, we increase the convergency of the residual. The better minimization procedure (as concerns the convergency, but not as concerns the speed) is generally performed by using bandpp*npband=nband. Put bandpp=2 when istwfk=2 (the time spent in FFTs is divided by two).

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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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densty

Mnemonics: initial DENSity for each TYpe of atom
Characteristic: DEVELOP
Variable type: real array densty(ntypat)
Default is 0.0d0.

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_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_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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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 calculations 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.

• 0=> Occupations are written but never read.
• 1=> Occupations are read from I_DMFTOCCND, where I is the root for input files.
• 2=> Occupations are read from O_DMFTOCCND, where O is the root for output files.

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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 LDA iteration.

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dmft_solv
Mnemonics: Dynamical Mean Fied Theory: choice of SOLVer
Characteristic: DEVELOP
Variable type: real
Default is 0

Choice of solver for the Impurity model.

• 1=> LDA+U self-energy is used (for testing purpose)
• 2=> Hubbard one solver.

WARNING: Quantum Monte Carlo (QMC) solvers are not yet interfaced with the code. The present version of LDA+DMFT implemented here should NOT be used for correlated metals. Even of correlated (Mott) insulators, QMC is expected to be much more precise: Hubbard one is a approximation !

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dmft_tollc
Mnemonics: Dynamical Mean Fied Theory: Tolerance on Local Charge for convergency of the DMFT loop
Characteristic: DEVELOP
Variable type: real
Default is 0.00001

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 convergency of the DFT Loop, the DMFT Loop needs a better convergence criterion.

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dmftbandf
dmftbandi
Mnemonics: (to be described)
Characteristic: DEVELOP
Variable type: (to be described)
Default is 0

dmftbandi and dmftbandf are the first and last bands taken into account in the Projected Local Orbitals scheme of LDA+DMFT. They thus 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

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effmass
Mnemonics: EFFective MASS
Characteristic: DEVELOP
Variable type: real number
Default is one.

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 number
Default is zero.

Used only 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 number
Default is 0.25

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 parameter
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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fermie_nest
Mnemonics: FERMI Energy for printing the NESTing function
Characteristic:
Variable type: real parameter
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 parameter
Default is 112, except for VPP Fujitsu, for which the Default is 111, and for NEC, for which the default is 200. Moreover, if the FFTW3 library has been enabled, the default becomes 312, EXCEPT if usedmft is non-zero for at least one dataset.
Finally, If paral_kgb=1, fftalg is automatically set to 401, with the hightest precedence.

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.f), as well as when applied to densities and potentials (routine fourdp.f). 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 :

• 1=> use FFT routines written by S. Goedecker.
• 2=> use machine-dependent FFT algorithm, taken from the vendor library, if it exists and if it has been implemented. The bare fftalg=200 has little chance to be faster than fftalg=112, but it might be tried. Implementing library subroutines with fftalg/=200 has not yet been done. Currently implemented library subroutines (fftalg=200) are:
• on HP, z3dfft from Veclib;
• on DEC Alpha, zfft_3d from DXML;
• on NEC, ZFC3FB from ASL lib;
• on SGI, zfft3d from complib.sgimath
• 3=> use serial or multi-threaded FFTW fortran routines (http://www.fftw.org). Currently implemented with fftalg=300.
• 4=> use FFT routines written by S. Goedecker, 2002 version, that will be suited for MPI and OpenMP parallelism.
The second digit (B) is related to fourdp.f :
• 0=> only use Complex-to-complex FFT
• 1=> real-to-complex is also allowed (only coded for A==1)
The third digit (C) is related to fourwf.f :
• 0=> no use of zero padding
• 1=> use of zero padding (only coded for A==1 and A==4)
• 2=> use of zero padding, and also combines actual FFT operations (using 2 routines from S. Goedecker) with important pre- and post-processing operations, in order to maximize cache data reuse. This is very efficient for cache architectures. (coded for A==1 and A==4, but A==4 is not yet sufficiently tested)
Internal representation as ngfft(7).

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fftcache

Mnemonics: Fast Fourier Transform CACHE size
Characteristic: DEVELOP
Variable type: integer parameter
Default is 16. Not yet machine-dependent.

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

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fft_opt_lob
Mnemonics: Fast Fourier Transform parallelisation - OPTion for LOB algorithm
Characteristic: DEVELOP
Variable type: integer
Default is 1. If paral_kgb=1, default is 2.

Option for LOB algorithm, used in the band/FFT/k-point parallelisation, see npband, npfft, npkpt, and paral_kgb.

• =1 : old implementation
• =2 : new implementation : the calls to getghc are made in parallel on a set of bands nbdblock : the aim is to reduce the number of collective communications. This is not yet implemented in lobpcgwf.

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freqsusin

Mnemonics: FREQuencies for the SUSceptibility matrix : the INcrement
Characteristic: DEVELOP
Variable type: real parameter, positive or zero
Default is 0.0

Define, with freqsuslo, the series of imaginary frequencies at which the susceptibility matrix should be computed.
This is still under development.

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freqsuslo

Mnemonics: FREQuencies for the SUSceptibility matrix : the LOwest frequency
Characteristic: DEVELOP
Variable type: real parameter, positive or zero
Default is 0.0

Define, with freqsusin, the series of imaginary frequencies at which the susceptibility matrix should be computed.
This is still under development.

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

Only relevant if ieig2rf is non-zero, that is, if the user is performing performing second-order eigenvalue calcul ations using response-functions. Also, relevant only for non-zero wavevectors qpt

From the electron-phonon matrix elements at some wavevector only, it is not possible to determine the Debye-Wallercontribution : 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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gpu_linalg_limit
Mnemonics: GPU (Cuda): LINear ALGebra LIMIT
Characteristic:
Variable type: integer parameter
Default is 2000000.

Only relevant if use_gpu_cuda=1, that is, if ABINIT is used with CUDA functionality.

Use of linear algebra and matrix algebra on GPU is only efficient if the size of the involved matrices is large enough. The gpu_linalg_limit parameter defines the threshold above which linear (and matrix) algebra operations are done on the Graphics Processing Unit.
The considered matrix size is equal to:

• SIZE=(mpw*nspinor/ npspinor)* (npband*bandpp)**2

• When SIZE>=gpu_linalg_limit, wfoptalg parameter is automatically set to 14 which corresponds to the use of LOBPCG algorithm for the calculation of the eigenstates.

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idyson
Mnemonics: Integer giving the choice of method for the DYSON equation
Characteristic: DEVELOP
Variable type: integer parameter
Default is 1.

Choice for the method used to solve the Dyson equation in the calculation of the interacting susceptibility matrix or/and in the calculation of the ACFD exchange-correlation energy:

• idyson=1 : Solve the Dyson equation by direct matrix inversion
• idyson=2 : Solve the Dyson equation as a first-order differential equation with respect to the coupling constant lambda - only implemented for the RPA at the present stage (see header of dyson_de.f for details)
• idyson=3 : Calculate only the diagonal of the interacting susceptibility matrix by self-consistently computing the linear density change in response to a set of perturbations. Only implemented for the RPA at the present stage, and entirely experimental (see dyson_sc.f for details).

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ikhxc
Mnemonics: Integer option for KHXC = Hartree XC kernel
Characteristic:
Variable type: integer parameter
Default is 1.

Define the HXC kernel, in the cases for which it can be dissociated with the choice of the HXC functional given by ixc, namely the TD-DFT computation of excited states (iscf=-1), and the computation of the susceptibility matrix (for ACFD purposes). Options 2 to 6 are for the ACFD only.

• 0 => RPA for the TDDFT but no kernel for the ACFD (testing purposes).
• 1 => RPA for the TDDFT and ACFD.
• 2 => ALDA (PW92) for the ACFD
• 3 => PGG for the ACFD [M. Petersilka, U.J. Gossmann and E.K.U. Gross, PRL 76,1212 (1996)]
• 4 => BPG for the ACFD. This amounts to half the PGG kernel plus half the ALDA kernel for spin-compensated systems [K. Burke, M. Petersilka and E.K.U. Gross, in "Recent Advances in Density Functional Methods", Vol. III, edited by P. Fantucci and A. Bencini (World Scientific, Singapore, 2002)]
• 5 => Linear energy optimized kernel [J. Dobson and J. Wang, PRB 62, 10038 (2000)]
• 6 => Non-linear energy optimized kernel [J. Dobson and J. Wang, PRB 62, 10038 (2000)]

For ACFD-ALDA, BPG and energy optimized kernels are highly experimental and not tested yet !!! For ACFD calculations, a cut-off density has been defined for the ALDA, BPG and energy optimized kernels : let rhomin = userre*rhomax (where rhomax is the maximum density in space) ; then the actual density used to calculate the local part of these kernels at point r is max(rho(r),rhomin.

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intexact
Mnemonics: INTegration using an EXACT scheme
Characteristic: DEVELOP
Variable type: integer parameter
Default is 0.

Relates to the ACFD xc functionals only. If intexact > 0, the integration over the coupling constant will be performed analytically in the RPA and in the two-electron PGG approximation for the ACFD exchange-correlation energy. Otherwise, the integration over the coupling constant will be performed numerically (also see ndyson and idyson. Note that the program will stop in intexact > 0 and ikhxc/=1 (RPA) or ikhxc/=3 (PGG, with two electrons)

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

• 0=> do "usual" xc quadrature on fft grid
• 1=> do higher accuracy xc quadrature using fft grid and additional points at the centers of each cube (doubles number of grid points)--the high accuracy version is only valid for boxcut>=2. If boxcut < 2, the code stops.

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 automatice tests use intxc=1. Please, do not follow this historical choice for your production runs.

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etsfgroups
Mnemonics: ETSF I/O additional GROUPS of variables
Characteristic: DEVELOP
Variable type: integer parameter
Default is 0.

NOTE : NOT USED AT PRESENT (v5.3.0)

This variable is a bit-wise combination of what will be written into / read from a special WFK/DEN/POT file. The contents of the file follow the Nanoquanta/ETSF file format specifications.

Please check the "etsf_io" module of the ETSF I/O library for possible values.

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etsfmain
Mnemonics: ETSF I/O MAIN variable
Characteristic: DEVELOP
Variable type: integer parameter
Default is 0.

NOTE : NOT USED AT PRESENT (v5.3.0)

This variable tells what will be written into / read from a special WFK/DEN/POT file. The contents of the file follow the Nanoquanta/ETSF file format specifications.

Please check the "etsf_io" module of the ETSF I/O library for possible values.

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iprcch

Mnemonics: Integer for PReConditioning of CHarge response
Characteristic: DEVELOP
Variable type: integer parameter
Default is 2.If ionmov=4 and iscf=5,iprcch is automatically put to 3. If paral_kgb=1, iprcch is automatically put to 6.

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 :

• 0 => density not changed (fixed charge), forces not corrected
• 1 => density not changed, forces corrected with rigid ion hypothesis (atomic charge moved with atom)
• 2 => density changed and forces corrected with rigid ion hypothesis (atomic charge moves with atom)
• 3 => density changed and forces corrected with a different implementation of the rigid ion hypothesis
• 4 => density not changed, forces corrected with the use of Harris functional formula (*)
• 5 => density changed using D. Alfe 2nd-order algorithm (**), forces not corrected
• 6 => density changed using D. Alfe 2nd-order algorithm (**) and forces corrected with the use of Harris functional formula (*)
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 iprcch=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 iprcch.

(**)Note concerning the use of iprcch=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 convergency of the SCF cycle; Typically, vres2 (or nres2) has to be small enough (10-4...10-5).

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iprcfc
Mnemonics: Integer for PReConditioner of Force Constants
Characteristic: DEVELOP
Variable type: integer parameter
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 :

• 0 => hessian is the identity matrix
• 1 => hessian is 0.5 times the identity matrix
• 2 => hessian is 0.25 times the identity matrix
• -1=> hessian is twice the identity matrix
• ... (simply corresponding power of 2 times the identity matrix)
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 parameter
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 :

• 1 => "uniformrandom", delivered with ABINIT package (initially comes from numerical receipies).
• 2 => intrinsic Fortran 90 random number generator.
• 3 => "ZBQ" non-deterministic random number generator by R. Chandler and P. Northrop. (This was delivered for free at http://www.ucl.ac.uk/~ucakarc/work/index.html#code", but the latter address does not seem to work anymore. In any case, the initial copyright is not violated by the files/documentation present in the ABINIT package).
irandom=3 is strongly adviced when performing Molecular Dynamics restarts (avoids bias).

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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 repetition Rate

istatshft
Mnemonics: Integer for STATus file SHiFT

Characteristic: DEVELOP, NO_MULTI
Variable type: integer parameter
Default is 49, and 149 for Cray T3E (slow I/Os).Values lower than 10 may not work on some machines. Default istatshft 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 array istwfk(nkpt)
Default is 0 for all k points for GS calculations. 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.

• 1=> do NOT take advantage of the time-reversal symmetry
• 2=> use time-reversal symmetry for k=( 0 0 0 )
• 3=> use time-reversal symmetry for k=(1/2 0 0 )
• 4=> use time-reversal symmetry for k=( 0 0 1/2)
• 5=> use time-reversal symmetry for k=(1/2 0 1/2)
• 6=> use time-reversal symmetry for k=( 0 1/2 0 )
• 7=> use time-reversal symmetry for k=(1/2 1/2 0 )
• 8=> use time-reversal symmetry for k=( 0 1/2 1/2)
• 9=> use time-reversal symmetry for k=(1/2 1/2 1/2)
• 0=> (preprocessed) for each k point, choose automatically the appropriate time-reversal option when it is allowed, and chose istwfk=1 for all the other k points.
Note that the input variable "mkmem" also controls the wavefunction storage, but at the level of core memory versus disk space.

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ldgapp
Mnemonics: Lein-Dobson-Gross approximation
Characteristic: DEVELOP
Variable type: integer parameter
Default is 0.

Concern only the ACFD computation of the correlation energy (optdriver=3).
If ldgapp > 0, the Lein, Dobson and Gross first-order approximation to the correlation energy is also computed during the ACFD run. [See Lein, Dobson and Gross, J. Comput. Chem. 20,12 (1999)]. This is only implemented for the RPA, for the PGG kernel and for the linear energy optimized kernel at the present time.

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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 parameter
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.

• macro_uj=1 (and nsppol=2) Standard procedure to determine U on atom pawujat through a shift of the potential on both spin channels.
• macro_uj=1 (and nsppol=1) Non standand procedure to determine U from potential shift on atom pawujat (experimental).
• macro_uj=2 (and nsppol=2) Non standand procedure to determine U from potential shift on atom pawujat through a shift on spin channel 1 on this atom and the response on this channel (experimental).
• macro_uj=3 (and nsppol=2) Standand procedure to determine J from potential shift on spin channel 1 on atom pawujat and response on spin channel 2 (experimental).
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 postion).

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maxnsym
Mnemonics: MAXimum Number of SYMetries
Characteristic: DEVELOP
Variable type: integer parameter
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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mqgrid
Mnemonics: Maximum number of Q-space GRID points for pseudopotentials
Characteristic: DEVELOP
Variable type: integer parameter
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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nbandsus
Mnemonics: Number of BANDs to compute the SUSceptibility
Characteristic:
Variable type: integer parameter
Default is nband.

Number of bands to be used in the calculation of the susceptibility matrix (ACFD only).

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

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

• if wfoptalg=4, nbdblock defines the number of blocks (the number of bands in the block is then nband/nbdblock ).

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nctime
Mnemonics: NetCdf TIME between output of molecular dynamics informations
Characteristic: DEVELOP
Variable type: integer parameter
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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ndyson
Mnemonics: Number of points to be added for the solution of the DYSON equation
Characteristic:
Variable type: integer parameter
Default is -1.

Number of points to be added to lambda=0 and lambda=1 (that are always calculated for the integration ober the coupling constant lambda in the ACFD calculation of the exchange-correlation energy.

• ndyson=-1 : let the code decide how many points to use (presently, 3 points for idyson=1 or 3, and 9 points for idyson=2)
• ndyson=0 : only compute the non-interacting and fully-interacting susceptibility matrices.
• ndyson>0 : use ndyson more points in ]0,1[

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nfreqsus
Mnemonics: Number of FREQuencies for the SUSceptibility matrix
Characteristic: DEVELOP
Variable type: integer parameter
Default is 0

If 0, no computation of frequency-dependent susceptibility matrix. If 1 or larger, will read freqsuslo and freqsusin to define the frequencies (1 is currently the only value allowed)

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nloalg
Mnemonics: Non Local ALGorithm
Characteristic: DEVELOP
Variable type: integer variable
Default is 4 (norm-conserving psps) or 14 (PAW), except for the NEC where it is 2 (or 12).

Allows to choose the algorithm for non-local operator application. On super-scalar architectures, the Default nloalg=4/14 is the best, but you can save memory by using nloalg=-4.
More detailed explanations:

Units figure of nloalg:
- nloalg=?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.
- nloalg=?3 : same as nloalg==2, but the loop order is inverted.
- nloalg=?4 : same as nloalg==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.

Tens figure of nloalg:
- nloalg<10 : (k+G) vectors are not precomputed, in order to save memory space.
- nloalg>=10 : (k+G) vectors are precomputed, once per k-point.

Sign of nloalg:
Negative values of nloalg correspond positive ones, where the phase precomputation has been suppressed, in order to save memory space: 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, nloalg is an array nloalg(1:5), that also allows to initialize several internal variables (not documented):
- nloalg(1)=mod(nloalg,10)
- jump=nloalg(2)
- mblkpw=nloalg(3)
- mincat=nloalg(4)
- nloalg(5)=nloalg/10
However, only nloalg(1)+10*nloalg(5) is read as an input variable.

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nnsclo
Mnemonics: Number of Non-Self Consistent LOops
Characteristic: DEVELOP
Variable type: integer parameter
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 correspond 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.

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normpawu

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

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

• normpawu=0 : leave projector
• normpawu=1 : renormalize

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noseft
Mnemonics:
Characteristic:
Variable type:
Default is

TO BE DOCUMENTED

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noseinert
Mnemonics:
Characteristic:
Variable type:
Default is

TO BE DOCUMENTED

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

Needed only when iscf=7 or 17.

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

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np_slk
Mnemonics: Number of mpi Processors used for ScaLapacK calls
Characteristic: DEVELOP
Variable type: integer parameter
Default is 1000000

Only relevant (for Ground-State calculations) when paral_kgb=1 and LOBPCG algorithm is used.
When using Scalapack (or any similar Matrix Algebra library), it is well known that the efficiency of the eigenproblem resolution saturates as the number of CPU cores increases. It is better to use a smaller number of CPU cores for the LINALG calls.
This maximum number of cores can be set with np_slk.
A large number for np_slk (i.e. 1000000) means that all cores are used for the Linear Algebra calls.

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nscforder
Mnemonics: SCaling Function ORDER
Characteristic:
Variable type:
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 parameter
Default is 2. However, optforces is automatically set to 1 when toldff or tolrff are non-zero.

Allows to choose options for the calculation of forces.

• optforces=0 : the forces are set to zero, and many steps of the computation of forces are skipped
• optforces=1 : calculation of forces at each SCF iteration, allowing to use forces as criterion to stop the SCF cycles
• optforces=2 : calculation of forces at the end of the SCF iterations (like the stresses)

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optfreqsus
Mnemonics: OPTion for the generation of FREQuency grids for the SUSceptibility
Characteristic: DEVELOP
Variable type: integer parameter
Default is 2

Selects the type of frequency grid that will be used to compute ACFD energies, as follows:

• 0: use preassigned mesh (see defs_suscep module)
• nfreqsus= 2: pick-up 2 highest frequencies of H_2 mesh
• nfreqsus= 8: pick-up 8 frequencies inside Be_2 mesh, depending on freq1
• nfreqsus= 9: pick-up 9 frequencies inside H_2 mesh, depending on freq1
• nfreqsus=11: pick-up 11 highest frequencies of Be_2 mesh
• nfreqsus=16: use full He mesh
• nfreqsus=18: use full H_2 mesh
• nfreqsus=20: use full He mesh good up to 8 Ha
• nfreqsus=24: use full Be_2 mesh
• 1: create linear mesh and weights for quadrature by Taylor rule
• freqsusin=starting frequency
• freqsuslo=frequency increment
• 2: create mesh and weights using Gauss-Legendre quadrature

A first Gauss-Legendre mesh is built for interval [0,freqsuslo], then a second one is obtained by transforming the first for the [freqsuslo,+\infty[ interval. freqsusin may be use to compress or expand the mesh on the second interval (a value of 1.0 is adequate for most cases). For practical reasons, nfreqsus must be even.

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

• optnlxccc=1 : uses the old psp6cc.f routine, with inconsistent treatment of real-space derivatives of the core function (computed in this routine, while splined in the other parts of the code)
• optnlxccc=2 : consistent calculation derivatives, in the psp6cc_dhr.f routine from DHamann.

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

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 mininisation.
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, actually identical to the one in versions prior to 1.7
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, 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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Characteristic: DEVELOP
Variable type: real pawujrad has the 'LENGTH' characteristics.
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, pawujv has the 'ENERGY' characteristics.
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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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 flag
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 flag
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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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 setten 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
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 0.0E00 (to change)

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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suskxcrs
Mnemonics: SUSceptibility times KXC treated in real space
Characteristic: DEVELOP
Variable type: integer
Default is 0

Only relevant for the ACFD calculation of total energies. If suskxcrs=1, the XC kernel is not treated in reciprocal space, but combined with the susceptibility (chi_0), to avoid Kxc divergences where the density goes to zero (G. Onida & M. Gatti !)

Not applicable for RPA (as there should be a Kxc present). Initially tested for ikhxc==2 (ALDA).

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symmorphi
Mnemonics: SYMMORPHIc symmetry operations
Characteristic: DEVELOP, GW
Variable type: integer parameter
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

• tfkinfunc=1 : Thomas-Fermi kinetic functional (explicit functional of the density) is used instead of Kohn-Sham kinetic energy functional (implicit functional of the density through Kohn-Sham wavefunctions).
• tfkinfunc=2 : the Recursion Method is used in order to compute electronic density, entropy, Fermi energy and eigenvalues energy. This method computes the density without computing any orbital, is efficient at high temperature, with a efficient parallelization (almost perfect scalability). When that option is in use, the ecut input variable is no longer a convergence parameter ; ngfft becomes the main convergence parameter: you should adapt ecut for the ngfft grid you need (it is not yet automatically computed). Other convergence parameter are for the energetic values: recnrec, recptrott, recnpath. Since the convergence of the self-consistent cycle is determined directly by the convergence of the density: toldfe, toldff tolrff, tolvrs, tolwfr are not used, and are replaced by rectolden; the energetic values, except for the fermi energy, are only computed during the latest SFC cycle : the output file will show a jump of the total energy at the end, but it is not because of a bad convergence behavior. Computational speed can be improved by the use of recrcut and recgratio. The recursion method has not be tested in the case of non cubic cell or with the use of symmetries. In the recursion method the following variables are set to:
useylm=1,
userec=1.

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

Sets a tolerance for the ratio of differences of eigenenergies in the line minisation 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_slk
Mnemonics: USE ScaLapacK
Characteristic: DEVELOP
Variable type: integer parameter
Default is 0

If set to 1, enable the use of ScaLapack within LOBPCG.

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

If set to 1, enable the use of LDA+DMFT, see in particular the important variables dmft_solv, dmftbandi, dmftbandf, dmft_nwli, dmft_nwlo, dmft_tollc, and dmft_iter. 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). Only static calculations without relaxation or dynamics are possible. Relevant quantity from converged DMFT calculations are total energy and spectral function. Total and partail spectral functions can be obtained with prtdos=1 and can be found in files OUTSpFunc* (where OUT is the root for output files). (see Amadon, B., Lechermann, F., Georges, A., Jollet, F., Wehling, T. O., and Lichtenstein, A. I. Phys. Rev. B 77(20), (2008) and B Amadon 2012 J. Phys.: Condens. Matter 24 075604 )

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useria, userib, useric, userid, userie
Mnemonics: USER Integer variables A, B, C, D and E
Characteristic:
Variable type: integers
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, userrb, userrc, userrd, userre
Mnemonics: USER Real variables A, B, C, D, and E
Characteristic:
Variable type: real numbers
Default is 0.0 .

These are user-definable with the same purpose as useri.

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useylm
Mnemonics: USE YLM (the spherical harmonics)
Characteristic: DEVELOP
Variable type: integer parameter
Default is 0 for norm-conserving pseudopotential(s), 1 for Projector Augmented-Wave (PAW), 1 when the recursion method is used (tfkinfunc=1).

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:

Plmn(r)=Ylm(r)*pln(r)

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

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

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. Used only if vdw_xc=10,11.

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

Used only when Van der Waals DFT-D2 correction is activated (vdw_xc=5).
The DFT-D2 (S. Grimme approach) dispersion potential is implemented as 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_typfrag
Mnemonics: van der Waals TYPe of FRAGment
Characteristic: DEVELOP
Variable type: integer array vdw_typfrag(natom)
Default is 1*natom

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. Used only if vdw_xc=10,11.

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

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 comming 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. Used only if vdw_xc=10,11.

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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:

• 0: no correction.
• 1: apply vdW-DF1 (DRSLL) from Dion et al.
doi:10.1103/PhysRevLett.92.246401
• 2: apply vdw-DF2 (LMKLL) from Lee et al.
arXiv:1003.5255v1
• 5: apply vdw-DFT-D2 as proposed by S. Grimme (adding a semi-empirical dispersion potential)
Available only for ground-state calculations ; see vdw_tol variable to control convergency
J. Comp. Chem. 27, 1787 (2006)
• 10: evaluate the vdW correlation energy from maximally localized Wannier functions, as proposed by P. L. Silvestrelli, also known as vdW-WF1 method. doi:10.1103/PhysRevLett.100.053002, doi:10.1016/j.cpc.2011.11.003
• 11: evaluate the vdW correlation energy from maximally localized Wannier functions, as proposed by A. Ambrosetti and P. L. Silvestrelli, also known as vdW-WF2 method. doi:10.1103/PhysRevB.85.073101
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 parameter
Default is 0 when usepaw=0 (norm-conserving pseudopotentials),
10 when usepaw=1 (PAW).
Default is 14 if paral_kgb=1.

Allows 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 1.0e-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 all 99.99d0

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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