ABINIT, basic input variables:
List and description.
This document lists and provides the description
of the name (keywords) of the "basic" input
variables 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/Infos/tuning file might be useful. For response-function calculations using
abinit, the complementary file ~ABINIT/Infos/respfn_help is needed.
Copyright (C) 1998-2012 ABINIT group (DCA, XG, RC)
This file is distributed under the terms of the GNU General Public License, see
~ABINIT/COPYING or
http://www.gnu.org/copyleft/gpl.txt .
For the initials of contributors, see ~ABINIT/Infos/contributors .
Content of the file : alphabetical list of "basic" variables.
A.
acell
angdeg
B.
C.
D.
E.
ecut
F.
G.
H.
I.
iscf
ixc
J.
jdtset
K.
kpt
kptnrm
kptopt
L.
M.
N.
natom
nband
ndtset
ngkpt
nkpt
nshiftk
nsppol
nstep
nsym
ntypat
O.
occopt
P.
Q.
R.
rprim
S.
scalecart
shiftk
symrel
T.
tnons
toldfe
toldff
tolrff
tolvrs
tolwfr
typat
U.
udtset
usewvl
V.
W.
wtk
wvl_hgrid
X.
xangst
xcart
xred
Y.
Z.
znucl
acell
Mnemonics: CELL lattice vector scaling
Characteristic: EVOLVING,LENGTH
Variable type: real array acell(3), represented internally as acell(3,nimage)
Default is 3*1 (in Bohr).
Gives the length scales by which
dimensionless primitive translations (in rprim) are
to be multiplied. By default, given in Bohr atomic units
(1 Bohr=0.5291772108 Angstroms), although Angstrom can be specified,
if preferred, since acell has the
'LENGTH' characteristics.
See further description of acell related to the
rprim input variable,
the scalecart input variable,
and the associated internal rprimd input variable.
Note that acell is NOT the length of the conventional orthogonal basis vectors, but the scaling factors of the primitive vectors.
Use scalecart to scale the cartesian coordinates.
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| Complete list of input variables
angdeg
Mnemonics: ANGles in DEGrees
Characteristic: NOT INTERNAL
Variable type: real array angdeg(3)
Default is No Default (use rprim as Default).
Gives the angles between directions of
primitive vectors of the unit cell (in degrees),
as an alternative to the input array rprim .
Will be used to set up rprim,
that, together with the array acell, will be used to define the
primitive vectors.
- angdeg(1) is the angle between the 2nd and 3rd vectors,
- angdeg(2) is the angle between the 1st and 3rd vectors,
- angdeg(3) is the angle between the 1st and 2nd vectors,
If the three angles are equal within 1.0d-12 (except if they are exactly 90 degrees),
the three primitive
vectors are chosen so that the trigonal symmetry that exchange
them is along the z cartesian axis :
R1=( a , 0,c)
R2=(-a/2, sqrt(3)/2*a,c)
R3=(-a/2,-sqrt(3)/2*a,c)
where a^{2}+c^{2}=1.0d0
If the angles are not all equal (or if they are all 90 degrees), one will have the following
generic form :
- R1=(1,0,0)
- R2=(a,b,0)
- R3=(c,d,e)
where each of the vectors is normalized,
and form the desired angles with the others.
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| Complete list of input variables
ecut
Mnemonics: Energy CUToff
Characteristic: ENERGY
Variable type: real parameter
Used for kinetic energy cutoff
which controls number
of planewaves at given k point by:
(1/2)[(2 Pi)*(k+Gmax)]^{2}=ecut for Gmax.
All planewaves inside this "basis sphere" centered
at k are included in the basis (except if dilatmx
is defined).
Can be specified in Ha (the default), Ry, eV or Kelvin, since
ecut has the
'ENERGY' characteristics.
(1 Ha=27.2113845 eV)
This is the single parameter which can have an enormous
effect on the quality of a calculation; basically the larger
ecut is, the better converged the calculation is. For fixed
geometry, the total energy MUST always decrease as ecut is
raised because of the variational nature of the problem.
Usually one runs at least several calculations at various ecut
to investigate the convergence needed for reliable results.
For k-points whose coordinates are build from 0 or 1/2,
the implementation of time-reversal symmetry that links
coefficients of the wavefunctions in reciprocal space
has been realized. See the input variable istwfk.
If activated (which corresponds to the Default mode),
this input variable istwfk will allow to
divide the number of plane wave (npw) treated explicitly
by a factor of two. Still, the final result should be identical with
the 'full' set of plane waves.
See the input variable ecutsm, for the
smoothing of the kinetic energy, needed to optimize unit cell parameters.
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| Complete list of input variables
iscf
Mnemonics: Integer for Self-Consistent-Field cycles
Characteristic:
Variable type: integer parameter
Default is 7 (norm-conserving), 17 (PAW) or 0 (WVL). (prior to v5.3 : 5 and 14)
Controls the self-consistency.
Positive values =>
this is the usual choice for doing the usual ground state (GS)
calculations or for structural relaxation, where
the potential has to be determined self-consistently.
The choice between different algorithms for SCF is possible :
- =0 => SCF cycle, direct minimization scheme on the gradient of the wavefunctions. This algorithm is faster than diagonalisation and mixing but is working only for systems with a gap. It is implemented only on the wavelet basis set, when usewvl=1.
- =1 => get the largest eigenvalue of the SCF cycle
(DEVELOP option, used with
irdwfk=1 or
irdwfq=1)
- =2 => SCF cycle, simple mixing of the potential
- =3 => SCF cycle, Anderson mixing of the potential
- =4 => SCF cycle, Anderson mixing of the potential based on the two previous iterations
- =5 => SCF cycle, CG based on the minim. of the energy with respect to the potential
- =7 => SCF cycle, Pulay mixing of the potential based on the npulayit previous iterations
- =12 => SCF cycle, simple mixing of the density
- =13 => SCF cycle, Anderson mixing of the density
- =14 => SCF cycle, Anderson mixing of the density based on the two previous iterations
- =15 => SCF cycle, CG based on the minim. of the energy with respect to the density
- =17 => SCF cycle, Pulay mixing of the density based on the npulayit previous iterations
- Other positive values, including zero ones, are not allowed.
Such algorithms for treating the "SCF iteration history" should be coupled with accompanying algorithms
for the SCF "preconditioning". See the input variable iprcel.
The default value iprcel=0 is often a good choice, but
for inhomogeneous systems, you might gain a lot with iprcel=45.
(Warning : if iscf>10, at present (v4.6), the energy printed at each SCF cycle is not variational -
this should not affect the other properties, and at convergence, all values are OK)
- In the norm-conserving case,
the default option is iscf=7, which is a compromise between speed and reliability.
The value iscf= 2 is safer but slower.
- In the PAW case, default option is iscf=17.
In PAW you have the possibility to mix density/potential on the fine or coarse FFT grid (see pawmixdg).
- Note that a Pulay mixing (iscf=7 or 17) with npulayit
=1 (resp. 2) is equivalent to an Anderson mixing with iscf=3 or 13 (resp. 4 or 14).
- Also note that:
* when mixing is done on potential (iscf<10), total energy is computed by "direct" decomposition.
* when mixing is done on density (iscf>=10), total energy is computed by "double counting" decomposition.
"Direct" and "double counting" decomposition of energy are equal when SCF cycle is converged. Note that,
when using GGA XC functionals, these decompositions of energy can be slighty different due
to imprecise computation of density gradients on FFT grid (difference decreases as size of FFT grid increases -
see ecut for NC pseudopotentials, pawecutdg for PAW).
Other (negative) options:
- = -2 =>
a non-self-consistent calculation is to be done;
in this case an electron density rho(r) on a real space grid
(produced in a previous calculation) will be read from a
disk file (automatically if ndtset=0, or
according to the value of getden
if ndtset/=0).
The name of the density file must be given as indicated
in the section 4 of abinit_help.
iscf=-2 would be used for
band structure calculations, to permit computation of
the eigenvalues of occupied and unoccupied states at
arbitrary k points in the fixed self consistent potential
produced by some integration grid of k points.
Due to this typical use, ABINIT insist that either
prtvol>2 or
prteig does not vanish
when there are more than 50 k points.
To compute the eigenvalues
(and wavefunctions) of unoccupied states in a separate
(non-selfconsistent) run, the user should
save the self-consistent rho(r)
and then run iscf=-2 for the intended set of k-points and bands.
To prepare a run with iscf=-2, a density file
can be produced using the
parameter prtden (see its description).
When a self-consistent set of wavefunctions is already available,
abinit can be used with
nstep=0 (see Test_v2/t47.in),
and the adequate value of prtden.
- = -3 =>
like -2, but initialize occ and wtk,
directly or indirectly (using ngkpt or
kptrlatt)
depending on the value of occopt.
For GS, this option
might be used to generate Density-of-states
(thanks to prtdos),
or to produce STM charge density map (thanks to prtstm).
For RF, this option is needed to compute the response to ddk perturbation.
- = -1 => like -2, but the non-self-consistent calculation
is followed by the determination of excited states
within TDDFT. This is only possible for nkpt=1,
with kpt=0 0 0.
Note that the oscillator strength needs to be defined with respect to
an origin of coordinate, thanks to the input variable
boxcenter. The maximal
number of Kohn-Sham excitations to be used to build the
excited state TDDFT matrix can be defined by td_mexcit,
or indirectly by the maximum Kohn-Sham excitation energy
td_maxene.
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| Complete list of input variables
ixc
Mnemonics: Integer for eXchange-Correlation choice
Characteristic:
Variable type: integer parameter
Default is ixc=1 (Teter parameterization). However, if all the pseudopotentials have the same value of pspxc, the initial value of ixc will be that common value.
Controls the choice of exchange and correlation (xc). The list of XC functionals is given
below. Positive values are for ABINIT native library of XC functionals, while negative values are for calling
the much wider set of functionals from the ETSF LibXC library (by M. Marques), also available at the
ETSF library Web page
Note that the choice made here should agree with the choice
made in generating the original pseudopotential, except
for ixc=0 (usually only used for debugging).
A warning is issued if this is not the case.
However, the choices ixc=1, 2, 3 and 7 are fits to the same data, from
Ceperley-Alder, and are rather similar, at least for spin-unpolarized systems.
The choice between the non-spin-polarized and spin-polarized case
is governed by the value of nsppol (see below).
Native ABINIT XC functionals
NOTE : in the implementation of the spin-dependence of these
functionals, and in order to avoid divergences in their
derivatives, the interpolating function between spin-unpolarized
and fully-spin-polarized function has been slightly modified,
by including a zeta rescaled by 1.d0-1.d-6. This should affect
total energy at the level of 1.d-6Ha, and should
have an even smaller effect on differences of energies, or derivatives.
The value ixc=10 is used internally : gives the difference between ixc=7 and
ixc=9, for use with an accurate RPA correlation energy.
- 1=> LDA or LSD, Teter Pade parametrization (4/93, published in S. Goedecker, M. Teter, J. Huetter, Phys.Rev.B54, 1703 (1996)), which
reproduces Perdew-Wang (which reproduces Ceperley-Alder!).
- 2=> LDA, Perdew-Zunger-Ceperley-Alder (no spin-polarization)
- 3=> LDA, old Teter rational polynomial parametrization (4/91)
fit to Ceperley-Alder data (no spin-polarization)
- 4=> LDA, Wigner functional (no spin-polarization)
- 5=> LDA, Hedin-Lundqvist functional (no spin-polarization)
- 6=> LDA, "X-alpha" functional (no spin-polarization)
- 7=> LDA or LSD, Perdew-Wang 92 functional
- 8=> LDA or LSD, x-only part of the Perdew-Wang 92 functional
- 9=> LDA or LSD, x- and RPA correlation part of the Perdew-Wang 92 functional
- 11=> GGA, Perdew-Burke-Ernzerhof GGA functional
- 12=> GGA, x-only part of Perdew-Burke-Ernzerhof GGA functional
- 13=> GGA potential of van Leeuwen-Baerends, while for energy, Perdew-Wang 92 functional
- 14=> GGA, revPBE of Y. Zhang and W. Yang, Phys. Rev. Lett. 80, 890 (1998)
- 15=> GGA, RPBE of B. Hammer, L.B. Hansen and J.K. Norskov, Phys. Rev. B 59, 7413 (1999)
- 16=> GGA, HTCH93 of F.A. Hamprecht, A.J. Cohen, D.J. Tozer, N.C. Handy, J. Chem. Phys. 109, 6264 (1998)
- 17=> GGA, HTCH120 of A.D. Boese, N.L. Doltsinis, N.C. Handy, and M. Sprik, J. Chem. Phys 112, 1670 (1998) - The usual HCTH functional.
- 18=> (NOT AVAILABLE : used internally for GGA BLYP pseudopotentials from
M. Krack, see Theor. Chem. Acc. 114, 145 (2005),
available from the CP2K repository
- use the LibXC instead, with ixc=-106131.
- 19=> (NOT AVAILABLE : used internally for GGA BP86 pseudopotentials from
M. Krack, see Theor. Chem. Acc. 114, 145 (2005),
available from the CP2K repository
- use the LibXC instead, with ixc=-106132.
- 20=> Fermi-Amaldi xc ( -1/N Hartree energy, where N is the
number of electrons per cell ; G=0 is not taken
into account however), for TDDFT tests.
No spin-pol. Does not work for RF.
- 21=> same as 20, except that the xc-kernel is the LDA (ixc=1) one,
for TDDFT tests.
- 22=> same as 20, except that the xc-kernel is the Burke-Petersilka-Gross
hybrid, for TDDFT tests.
- 23=> GGA of Z. Wu and R.E. Cohen, Phys. Rev. 73, 235116 (2006).
- 24=> GGA, C09x exchange of V. R. Cooper, PRB 81, 161104(R) (2010).
- 26=> GGA, HTCH147 of A.D. Boese, N.L. Doltsinis, N.C. Handy, and M. Sprik, J. Chem. Phys 112, 1670 (1998).
- 27=> GGA, HTCH407 of A.D. Boese, and N.C. Handy, J. Chem. Phys 114, 5497 (2001).
- 28=> (NOT AVAILABLE : used internally for GGA OLYP pseudopotentials from
M. Krack, see Theor. Chem. Acc. 114, 145 (2005),
available from the CP2K repository
- use the LibXC instead, with ixc=-110131.
ETSF Lib XC functionals
Note that you must compile ABINIT with the LibXC plug-in in order to be able to access these functionals.
The LibXC functionals are accessed by negative values of ixc.
The LibXC contains functional forms for either exchange-only functionals, correlation-only functionals,
or combined exchange and correlation functionals. Each of them is to be specified by a three-digit number.
In case of a combined exchange and correlation functional, only one such three-digit number has to be specified as value of ixc,
with a minus sign (to indicate that it comes from the LibXC).
In the case of separate exchange functional (let us represent its identifier by XXX) and
correlation functional (let us represent its identified by CCC),
a six-digit number will have to be specified for ixc, by concatenation, be it XXXCCC or CCCXXX.
As an example, ixc=-020 gives access to the Teter93 LDA, while
ixc=-101130 gives access to the PBE GGA.
In version 0.9 of LibXC (December 2008), there are 16 three-dimensional (S)LDA functionals (1 for X, 14 for C, 1 for combined XC),
and there are 41 three-dimensional GGA (23 for X, 8 for C, 10 for combined XC).
Note that for a meta-GGA, the kinetic energy density is needed. This means having usekden=1 .
(S)LDA functionals (do not forget to add a minus sign, as discussed above)
- 001=> XC_LDA_X
[PAM Dirac, Proceedings of the Cambridge Philosophical Society 26, 376 (1930);
F Bloch, Zeitschrift fuer Physik 57, 545 (1929)
]
- 002=> XC_LDA_C_WIGNER Wigner parametrization
[EP Wigner, Trans. Faraday Soc. 34, 678 (1938)
]
- 003=> XC_LDA_C_RPA Random Phase Approximation
[M Gell-Mann and KA Brueckner, Phys. Rev. 106, 364 (1957)
]
- 004=> XC_LDA_C_HL Hedin & Lundqvist
[L Hedin and BI Lundqvist, J. Phys. C 4, 2064 (1971)
]
- 005=> XC_LDA_C_GL ! Gunnarson & Lundqvist
[O Gunnarsson and BI Lundqvist, PRB 13, 4274 (1976)
]
- 006=> XC_LDA_C_XALPHA ! Slater's Xalpha
]
- 007=> XC_LDA_C_VWN ! Vosko, Wilk, & Nussair
[SH Vosko, L Wilk, and M Nusair, Can. J. Phys. 58, 1200 (1980)
]
- 008=> XC_LDA_C_VWN_RPA ! Vosko, Wilk, & Nussair (RPA)
[SH Vosko, L Wilk, and M Nusair, Can. J. Phys. 58, 1200 (1980)
]
- 009=> XC_LDA_C_PZ ! Perdew & Zunger
[Perdew and Zunger, Phys. Rev. B 23, 5048 (1981)
]
- 010=> XC_LDA_C_PZ_MOD ! Perdew & Zunger (Modified)
[Perdew and Zunger, Phys. Rev. B 23, 5048 (1981)
Modified to improve the matching between the low and high rs part
]
- 011=> XC_LDA_C_OB_PZ ! Ortiz & Ballone (PZ)
[G Ortiz and P Ballone, Phys. Rev. B 50, 1391 (1994) ;
G Ortiz and P Ballone, Phys. Rev. B 56, 9970(E) (1997) ;
Perdew and Zunger, Phys. Rev. B 23, 5048 (1981)
]
- 012=> XC_LDA_C_PW ! Perdew & Wang
[JP Perdew and Y Wang, Phys. Rev. B 45, 13244 (1992)
]
- 013=> XC_LDA_C_PW_MOD ! Perdew & Wang (Modified)
[JP Perdew and Y Wang, Phys. Rev. B 45, 13244 (1992) ;
Added extra digits to some constants as in the PBE routine
see http://www.chem.uci.edu/~kieron/dftold2/pbe.php
(at some point it was available at http://dft.uci.edu/pbe.php)
]
- 014=> XC_LDA_C_OB_PW ! Ortiz & Ballone (PW)
[G Ortiz and P Ballone, Phys. Rev. B 50, 1391 (1994) ;
G Ortiz and P Ballone, Phys. Rev. B 56, 9970(E) (1997) ;
JP Perdew and Y Wang, Phys. Rev. B 45, 13244 (1992)
]
- 017=> XC_LDA_C_vBH ! von Barth & Hedin
[U von Barth and L Hedin, J. Phys. C: Solid State Phys. 5, 1629 (1972)
]
- 020=> XC_LDA_XC_TETER93 ! Teter 93 parametrization
[S Goedecker, M Teter, J Hutter, PRB 54, 1703 (1996)
]
- 022=> XC_LDA_C_ML1 ! Modified LSD (version 1) of Proynov and Salahub
[EI Proynov and D Salahub, Phys. Rev. B 49, 7874 (1994)
]
- 023=> XC_LDA_C_ML2 ! Modified LSD (version 2) of Proynov and Salahub
[EI Proynov and D Salahub, Phys. Rev. B 49, 7874 (1994)
]
- 024=> XC_LDA_C_GOMBAS ! Gombas parametrization
[P. Gombas, Pseudopotentials (Springer-Verlag, New York, 1967)
]
GGA functionals (do not forget to add a minus sign, as discussed above)
- 101=> XC_GGA_X_PBE ! Perdew, Burke & Ernzerhof exchange
[JP Perdew, K Burke, and M Ernzerhof, Phys. Rev. Lett. 77, 3865 (1996) ;
JP Perdew, K Burke, and M Ernzerhof, Phys. Rev. Lett. 78, 1396(E) (1997)
]
- 102=> XC_GGA_X_PBE_R ! Perdew, Burke & Ernzerhof exchange (revised)
[Y Zhang and W Yang, Phys. Rev. Lett 80, 890 (1998)
]
- 103=> XC_GGA_X_B86 ! Becke 86 Xalfa,beta,gamma
[AD Becke, J. Chem. Phys 84, 4524 (1986)
]
- 104=> XC_GGA_X_HERMAN ! Herman Xalphabeta GGA
[F Herman, JP Van Dyke, and IB Ortenburger, Phys. Rev. Lett. 22, 807 (1969) ;
F Herman, IB Ortenburger, and JP Van Dyke, Int. J. Quantum Chem. Symp. 3, 827 (1970)
]
- 105=> XC_GGA_X_B86_MGC ! Becke 86 Xalfa,beta,gamma (with mod. grad. correction)
[AD Becke, J. Chem. Phys 84, 4524 (1986) ;
AD Becke, J. Chem. Phys 85, 7184 (1986)
]
- 106=> XC_GGA_X_B88 ! Becke 88
[AD Becke, Phys. Rev. A 38, 3098 (1988)
]
- 107=> XC_GGA_X_G96 ! Gill 96
[PMW Gill, Mol. Phys. 89, 433 (1996)
]
- 108=> XC_GGA_X_PW86 ! Perdew & Wang 86
[JP Perdew and Y Wang, Phys. Rev. B 33, 8800 (1986)
]
- 109=> XC_GGA_X_PW91 ! Perdew & Wang 91
[JP Perdew, in Proceedings of the 21st Annual International Symposium on the Electronic Structure of Solids, ed. by P Ziesche and H
Eschrig (Akademie Verlag, Berlin, 1991), p. 11. ;
JP Perdew, JA Chevary, SH Vosko, KA Jackson, MR Pederson, DJ Singh, and C Fiolhais, Phys. Rev. B 46, 6671 (1992) ;
JP Perdew, JA Chevary, SH Vosko, KA Jackson, MR Pederson, DJ Singh, and C Fiolhais, Phys. Rev. B 48, 4978(E) (1993)
]
- 110=> XC_GGA_X_OPTX ! Handy & Cohen OPTX 01
[NC Handy and AJ Cohen, Mol. Phys. 99, 403 (2001)
]
- 111=> XC_GGA_X_DK87_R1 ! dePristo & Kress 87 (version R1)
[AE DePristo and JD Kress, J. Chem. Phys. 86, 1425 (1987)
]
- 112=> XC_GGA_X_DK87_R2 ! dePristo & Kress 87 (version R2)
[AE DePristo and JD Kress, J. Chem. Phys. 86, 1425 (1987)
]
- 113=> XC_GGA_X_LG93 ! Lacks & Gordon 93
[DJ Lacks and RG Gordon, Phys. Rev. A 47, 4681 (1993)
]
- 114=> XC_GGA_X_FT97_A ! Filatov & Thiel 97 (version A)
[M Filatov and W Thiel, Mol. Phys 91, 847 (1997)
]
- 115=> XC_GGA_X_FT97_B ! Filatov & Thiel 97 (version B)
[M Filatov and W Thiel, Mol. Phys 91, 847 (1997)
]
- 116=> XC_GGA_X_PBE_SOL ! Perdew, Burke & Ernzerhof exchange (solids)
[JP Perdew, et al, Phys. Rev. Lett. 100, 136406 (2008)
]
- 117=> XC_GGA_X_RPBE ! Hammer, Hansen & Norskov (PBE-like)
[B Hammer, LB Hansen and JK Norskov, Phys. Rev. B 59, 7413 (1999)
]
- 118=> XC_GGA_X_WC ! Wu & Cohen
[Z Wu and RE Cohen, Phys. Rev. B 73, 235116 (2006)
]
- 119=> XC_GGA_X_mPW91 ! Modified form of PW91 by Adamo & Barone
[C Adamo and V Barone, J. Chem. Phys. 108, 664 (1998)
]
- 120=> XC_GGA_X_AM05 ! Armiento & Mattsson 05 exchange
[R Armiento and AE Mattsson, Phys. Rev. B 72, 085108 (2005) ;
AE Mattsson, R Armiento, J Paier, G Kresse, JM Wills, and TR Mattsson, J. Chem. Phys. 128, 084714 (2008)
]
- 121=> XC_GGA_X_PBEA ! Madsen (PBE-like)
[G Madsen, Phys. Rev. B 75, 195108 (2007)
]
- 122=> XC_GGA_X_MPBE ! Adamo & Barone modification to PBE
[C Adamo and V Barone, J. Chem. Phys. 116, 5933 (2002)
]
- 123=> XC_GGA_X_XPBE ! xPBE reparametrization by Xu & Goddard
[X Xu and WA Goddard III, J. Chem. Phys. 121, 4068 (2004)
]
- 125=> XC_GGA_X_BAYESIAN ! Bayesian best fit for the enhancement factor
[JJ Mortensen, K Kaasbjerg, SL Frederiksen, JK Norskov, JP Sethna, and KW Jacobsen, Phys. Rev. Lett. 95, 216401 (2005)
]
- 126=> XC_GGA_X_PBE_JSJR ! PBE JSJR reparametrization by Pedroza, Silva & Capelle
[LS Pedroza, AJR da Silva, and K. Capelle, Phys. Rev. B 79, 201106(R) (2009)
]
- 130=> XC_GGA_C_PBE ! Perdew, Burke & Ernzerhof correlation
[JP Perdew, K Burke, and M Ernzerhof, Phys. Rev. Lett. 77, 3865 (1996) ;
JP Perdew, K Burke, and M Ernzerhof, Phys. Rev. Lett. 78, 1396(E) (1997)
]
- 131=> XC_GGA_C_LYP ! Lee, Yang & Parr
[C Lee, W Yang and RG Parr, Phys. Rev. B 37, 785 (1988)
B Miehlich, A Savin, H Stoll and H Preuss, Chem. Phys. Lett. 157, 200 (1989)
]
- 132=> XC_GGA_C_P86 ! Perdew 86
[JP Perdew, Phys. Rev. B 33, 8822 (1986)
]
- 133=> XC_GGA_C_PBE_SOL ! Perdew, Burke & Ernzerhof correlation SOL
[JP Perdew, et al, Phys. Rev. Lett. 100, 136406 (2008)
]
- 134=> XC_GGA_C_PW91 ! Perdew & Wang 91
[JP Perdew, JA Chevary, SH Vosko, KA Jackson, MR Pederson, DJ Singh, and C Fiolhais, Phys. Rev. B 46, 6671 (1992)
]
- 135=> XC_GGA_C_AM05 ! Armiento & Mattsson 05 correlation
[ R Armiento and AE Mattsson, Phys. Rev. B 72, 085108 (2005) ;
AE Mattsson, R Armiento, J Paier, G Kresse, JM Wills, and TR Mattsson, J. Chem. Phys. 128, 084714 (2008)
]
- 136=> XC_GGA_C_XPBE ! xPBE reparametrization by Xu & Goddard
[X Xu and WA Goddard III, J. Chem. Phys. 121, 4068 (2004)
]
- 137=> XC_GGA_C_LM ! Langreth and Mehl correlation
[DC Langreth and MJ Mehl, Phys. Rev. Lett. 47, 446 (1981)
]
- 138=> XC_GGA_C_PBE_JRGX ! JRGX reparametrization by Pedroza, Silva & Capelle
[LS Pedroza, AJR da Silva, and K. Capelle, Phys. Rev. B 79, 201106(R) (2009)
]
- 139=> XC_GGA_X_OPTB88_VDW ! Becke 88 reoptimized to be used with vdW functional of Dion et al
[J Klimes, DR Bowler, and A Michaelides, J. Phys.: Condens. Matter 22, 022201 (2010)
]
- 140=> XC_GGA_X_PBEK1_VDW ! PBE reparametrization for vdW
[J Klimes, DR Bowler, and A Michaelides, J. Phys.: Condens. Matter 22, 022201 (2010)
]
- 141=> XC_GGA_X_OPTPBE_VDW ! PBE reparametrization for vdW
[J Klimes, DR Bowler, and A Michaelides, J. Phys.: Condens. Matter 22, 022201 (2010)
]
- 142=> XC_GGA_X_RGE2 ! Regularized PBE
[A Ruzsinszky, GI Csonka, and G Scuseria, J. Chem. Theory Comput. 5, 763 (2009)
]
- 143=> XC_GGA_C_RGE2 ! Regularized PBE
[A Ruzsinszky, GI Csonka, and G Scuseria, J. Chem. Theory Comput. 5, 763 (2009)
]
- 144=> XC_GGA_X_RPW86 ! refitted Perdew & Wang 86
[ED Murray, K Lee and DC Langreth, J. Chem. Theory Comput. 5, 2754-2762 (2009)
]
- 145=> XC_GGA_X_KT1 ! Keal and Tozer version 1
[TW Keal and DJ Tozer, J. Chem. Phys. 119, 3015 (2003)
]
- 146=> XC_GGA_XC_KT2 ! Keal and Tozer version 2
[TW Keal and DJ Tozer, J. Chem. Phys. 119, 3015 (2003)
]
- 147=> XC_GGA_C_WL ! Wilson & Levy
[LC Wilson and M Levy, Phys. Rev. B 41, 12930 (1990)
]
- 148=> XC_GGA_C_WI ! Wilson & Ivanov
[LC Wilson & S Ivanov, Int. J. Quantum Chem. 69, 523-532 (1998)
]
- 149=> XC_GGA_X_MB88 ! Modified Becke 88 for proton transfer
[V Tognetti and C Adamo, J. Phys. Chem. A 113, 14415-14419 (2009)
]
- 161=> XC_GGA_XC_HCTH_93 ! HCTH functional fitted to 93 molecules
[FA Hamprecht, AJ Cohen, DJ Tozer, and NC Handy, J. Chem. Phys. 109, 6264 (1998)
]
- 162=> XC_GGA_XC_HCTH_120 ! HCTH functional fitted to 120 molecules
[AD Boese, NL Doltsinis, NC Handy, and M Sprik, J. Chem. Phys. 112, 1670 (2000)
]
- 163=> XC_GGA_XC_HCTH_147 ! HCTH functional fitted to 147 molecules
[AD Boese, NL Doltsinis, NC Handy, and M Sprik, J. Chem. Phys. 112, 1670 (2000)
]
- 164=> XC_GGA_XC_HCTH_407 ! HCTH functional fitted to 407 molecules
[AD Boese, and NC Handy, J. Chem. Phys. 114, 5497 (2001)
]
- 165=> XC_GGA_XC_EDF1 ! Empirical functionals from Adamson, Gill, and Pople
[RD Adamson, PMW Gill, and JA Pople, Chem. Phys. Lett. 284 6 (1998)
]
- 166=> XC_GGA_XC_XLYP ! XLYP functional
[X Xu and WA Goddard, III, PNAS 101, 2673 (2004)
]
- 167=> XC_GGA_XC_B97 ! Becke 97
[AD Becke, J. Chem. Phys. 107, 8554-8560 (1997)
]
- 168=> XC_GGA_XC_B97_1 ! Becke 97-1
[FA Hamprecht, AJ Cohen, DJ Tozer, and NC Handy, J. Chem. Phys. 109, 6264 (1998);
AD Becke, J. Chem. Phys. 107, 8554-8560 (1997)
]
- 169=> XC_GGA_XC_B97_2 ! Becke 97-2
[AD Becke, J. Chem. Phys. 107, 8554-8560 (1997)
]
- 170=> XC_GGA_XC_B97_D ! Grimme functional to be used with C6 vdW term
[S Grimme, J. Comput. Chem. 27, 1787 (2006)
]
- 171=> XC_GGA_XC_B97_K ! Boese-Martin for Kinetics
[AD Boese and JML Martin, J. Chem. Phys., Vol. 121, 3405 (2004)
]
- 172=> XC_GGA_XC_B97_3 ! Becke 97-3
[TW Keal and DJ Tozer, J. Chem. Phys. 123, 121103 (2005)
]
- 173=> XC_GGA_XC_PBE1W ! Functionals fitted for water
[EE Dahlke and DG Truhlar, J. Phys. Chem. B 109, 15677 (2005)
]
- 174=> XC_GGA_XC_MPWLYP1W ! Functionals fitted for water
[EE Dahlke and DG Truhlar, J. Phys. Chem. B 109, 15677 (2005)
]
- 175=> XC_GGA_XC_PBELYP1W ! Functionals fitted for water
[EE Dahlke and DG Truhlar, J. Phys. Chem. B 109, 15677 (2005)
]
- 176=> XC_GGA_XC_SB98_1a ! Schmider-Becke 98 parameterization 1a
[HL Schmider and AD Becke, J. Chem. Phys. 108, 9624 (1998)
]
- 177=> XC_GGA_XC_SB98_1b ! Schmider-Becke 98 parameterization 1b
[HL Schmider and AD Becke, J. Chem. Phys. 108, 9624 (1998)
]
- 178=> XC_GGA_XC_SB98_1c ! Schmider-Becke 98 parameterization 1c
[HL Schmider and AD Becke, J. Chem. Phys. 108, 9624 (1998)
]
- 179=> XC_GGA_XC_SB98_2a ! Schmider-Becke 98 parameterization 2a
[HL Schmider and AD Becke, J. Chem. Phys. 108, 9624 (1998)
]
- 180=> XC_GGA_XC_SB98_2b ! Schmider-Becke 98 parameterization 2b
[HL Schmider and AD Becke, J. Chem. Phys. 108, 9624 (1998)
]
- 181=> XC_GGA_XC_SB98_2c ! Schmider-Becke 98 parameterization 2c
[HL Schmider and AD Becke, J. Chem. Phys. 108, 9624 (1998)
]
- 183=> XC_GGA_X_OL2 ! Exchange form based on Ou-Yang and Levy v.2
[P Fuentealba and O Reyes, Chem. Phys. Lett. 232, 31-34 (1995) ; H Ou-Yang, M Levy, Int. J. of Quant. Chem. 40, 379-388 (1991)
]
- 184=> XC_GGA_X_APBE ! mu fixed from the semiclassical neutral atom
[LA Constantin, E Fabiano, S Laricchia, and F Della Sala, Phys. Rev. Lett. 106, 186406 (2011)
]
- 186=> XC_GGA_C_APBE ! mu fixed from the semiclassical neutral atom
[LA Constantin, E Fabiano, S Laricchia, and F Della Sala, Phys. Rev. Lett. 106, 186406 (2011)
]
- 202=> XC_MGGA_X_TPSS ! Tao, Perdew, Staroverov & Scuseria
[J Tao, JP Perdew, VN Staroverov, and G Scuseria, Phys. Rev. Lett. 91, 146401 (2003) ;
JP Perdew, J Tao, VN Staroverov, and G Scuseria, J. Chem. Phys. 120, 6898 (2004)
]
- 203=> XC_MGGA_X_M06L ! Zhao, Truhlar exchange
[Y Zhao and DG Truhlar, JCP 125, 194101 (2006);
Y Zhao and DG Truhlar, Theor. Chem. Account 120, 215 (2008)
]
- 204=> XC_MGGA_X_GVT4 ! GVT4 (X part of VSXC) from van Voorhis and Scuseria
[T Van Voorhis and GE Scuseria, JCP 109, 400 (1998)
]
- 205=> XC_MGGA_X_TAU_HCTH ! tau-HCTH from Boese and Handy
[AD Boese and NC Handy, JCP 116, 9559 (2002)
]
- 207=> XC_MGGA_X_BJ06 ! Becke & Johnson correction to Becke-Roussel 89
[AD Becke and ER Johnson, J. Chem. Phys. 124, 221101 (2006)
] WARNING : this Vxc-only mGGA can only be used with a LDA correlation, typically Perdew-Wang 92.
- 208=> XC_MGGA_X_TB09 ! Tran-blaha - correction to Becke & Johnson correction to Becke-Roussel 89
[F Tran and P Blaha, Phys. Rev. Lett. 102, 226401 (2009)
] WARNING : this Vxc-only mGGA can only be used with a LDA correlation, typically Perdew-Wang 92.
- 209=> XC_MGGA_X_RPP09 ! Rasanen, Pittalis, and Proetto correction to Becke & Johnson
[E Rasanen, S Pittalis & C Proetto, arXiv:0909.1477 (2009)
] WARNING : this Vxc-only mGGA can only be used with a LDA correlation, typically Perdew-Wang 92.
- 232=> XC_MGGA_C_VSXC ! VSxc from Van Voorhis and Scuseria (correlation part)
[T Van Voorhis and GE Scuseria, JCP 109, 400 (1998)
]
Go to the top
| Complete list of input variables
jdtset
Mnemonics: index -J- for DaTaSETs
Characteristic: NO MULTI
Variable type: integer array jdtset(ndtset)
Default is the series 1, 2, 3 ... ndtset .
Gives the dataset index
of each of the datasets. This index will be used :
- to determine which input variables are specific to each
dataset, since the variable names for this
dataset will be made from the bare variable
name concatenated with this index, and only if
such a composite variable name does not exist,
the code will consider the bare variable name,
or even, the Default;
- to characterize output variable names, if their
content differs from dataset to dataset;
- to characterize output files ( root names appended with _DSx
where 'x' is the dataset index ).
The allowed index values are between 1 and 9999.
An input variable name appended with 0 is not allowed.
When ndtset==0, this array is not used, and moreover,
no input variable name appended with a digit is allowed.
This array might be initialized thanks to the use of
the input variable udtset. In this case, jdtset cannot
be used.
Go to the top
| Complete list of input variables
kpt
Mnemonics: K - PoinTs
Characteristic:
Variable type: real array kpt(3,nkpt)
Default is 0. 0. 0. (for just one k-point, adequate for one molecule in a supercell)
Contains the k points in terms
of reciprocal space primitive translations (NOT in
cartesian coordinates!).
Needed ONLY
if kptopt=0, otherwise
deduced from other input variables.
It contains dimensionless numbers in terms of which
the cartesian coordinates would be:
k_cartesian = k1*G1+k2*G2+k3*G3
where (k1,k2,k3) represent the dimensionless "reduced
coordinates" and G1, G2, G3 are the cartesian coordinates
of the primitive translation vectors. G1,G2,G3 are related
to the choice of direct space primitive translation vectors
made in rprim.
Note that an overall norm for the k
points is supplied by kptnrm. This allows
one to avoid supplying many digits for the k points to
represent such points as (1,1,1)/3.
Note: one of the algorithms used to set up the sphere
of G vectors for the basis needs components of k-points
in the range [-1,1], so the
remapping is easily done by adding or subtracting 1 from
each component until it is in the range [-1,1]. That is,
given the k point normalization kptnrm described below,
each component must lie in [-kptnrm,kptnrm].
Note: a global shift can be provided by qptn
Not read if kptopt/=0 .
Go to the top
| Complete list of input variables
kptnrm
Mnemonics: K - PoinTs NoRMalization
Characteristic:
Variable type: real parameter
Default is 1.
Establishes a normalizing denominator
for each k point.
Needed only
if kptopt<=0, otherwise
deduced from other input variables.
The k point coordinates as fractions
of reciprocal lattice translations are therefore
kpt(mu,ikpt)/kptnrm. kptnrm defaults to 1 and can
be ignored by the user. It is introduced to avoid
the need for many digits in representing numbers such as 1/3.
It cannot be smaller than 1.0d0
Go to the top
| Complete list of input variables
kptopt
Mnemonics: KPoinTs OPTion
Characteristic:
Variable type: integer parameter
Default is 1 (WARNING : was 0 prior to 5.8).
Controls the set up of the k-points list.
The aim will be to initialize, by straight reading
or by a preprocessing approach based on other input variables,
the following input variables, giving the k points, their number,
and their weight:
kpt,
kptnrm,
nkpt,
and, for iscf/=-2,
wtk.
Often, the k points will form a lattice in reciprocal space. In this case,
one will also aim at initializing input variables that give
the reciprocal of this k-point lattice, as well as its shift with respect
to the origin:
ngkpt or
kptrlatt,
as well as on nshiftk and
shiftk.
A global additional shift can be provided by qptn
- 0=> read directly nkpt, kpt,
kptnrm and wtk.
- 1=> rely on ngkpt or
kptrlatt, as well as on
nshiftk and
shiftk to set up the k points.
Take fully into account the symmetry to generate the
k points in the Irreducible Brillouin Zone only, with the appropriate weights.
(This is the usual mode for GS calculations)
- 2=> rely on
ngkpt or
kptrlatt, as well as on
nshiftk and
shiftk to set up the k points.
Take into account only the time-reversal symmetry :
k points will be generated in half the Brillouin zone, with the appropriate weights.
(This is to be used when preparing or executing a
RF calculation at q=(0 0 0) )
- 3=> rely on ngkpt or
kptrlatt, as well as on
nshiftk and
shiftk to set up the k points.
Do not take into account any symmetry :
k points will be generated in the full Brillouin zone, with the appropriate weights.
(This is to be used when preparing or executing a
RF calculation at non-zero q )
- 4=> rely on ngkpt or
kptrlatt, as well as on
nshiftk and
shiftk to set up the k points.
Take into account all the symmetries EXCEPT the time-reversal symmetry
to generate the k points in the Irreducible Brillouin Zone, with the appropriate weights.
This has to be used when performing PAW calculations including
spin-orbit coupling (pawspnorb/=0)
- A negative value =>
rely on kptbounds,
and ndivk
to set up a band structure calculation along different lines
(allowed only for iscf==-2).
The absolute value of kptopt gives the number of segments
of the band structure. Weights are usually irrelevant with this option, and will be left to their default value.
In the case of a grid of k points, the auxiliary variables
kptrlen,
ngkpt and
prtkpt might help
you to select the optimal grid.
Go to the top
| Complete list of input variables
natom
Mnemonics: Number of ATOMs
Characteristic:
Variable type: integer parameter
Default is 1
Gives the total number of atoms in the unit cell.
Default is 1 but you will obviously want to input this
value explicitly.
Note that natom refers to all atoms in the unit cell, not
only to the irreducible set of atoms in the unit cell (using symmetry operations,
this set allows to recover all atoms). If you want
to specify only the irreducible set of atoms, use the
symmetriser, see the input variable natrd.
Go to the top
| Complete list of input variables
nband
Mnemonics: Number of BANDs
Characteristic:
Variable type: integer parameter
Default is 1.
Gives number of bands, occupied plus
possibly unoccupied, for which wavefunctions are being computed
along with eigenvalues.
Note : if the parameter
occopt (see below) is not set to 2,
nband is a scalar integer, but
if the parameter occopt is set to 2,
then nband must be an array nband(nkpt*
nsppol) giving the
number of bands explicitly for each k point. This
option is provided in order to allow the number of
bands treated to vary from k point to k point.
For the values of occopt not equal to 0 or 2, nband
can be omitted. The number of bands will be set up
thanks to the use of the variable fband. The present Default
will not be used.
If nspinor is 2, nband must be even for
each k point.
In the case of a GW calculation (optdriver=3 or 4),
nband gives the number of bands to be treated to generate the screening (susceptibility
and dielectric matrix), as well as the self-energy. However, to generate the _KSS
file (see kssform)
the relevant number of bands is given by nbandkss.
Go to the top
| Complete list of input variables
ndtset
Mnemonics: Number of DaTaSETs
Characteristic: NO MULTI
Variable type: integer parameter
Default is 0 (no multi-data set).
Gives the number of data sets to be
treated.
If 0, means that the multi-data set treatment is not used,
so that the root filenames will not be appended with _DSx,
where 'x' is the dataset index defined
by the input variable jdtset,
and also that input names with a dataset index are not allowed.
Otherwise, ndtset=0 is equivalent to ndtset=1.
Go to the top
| Complete list of input variables
ngkpt
Mnemonics: Number of Grid points for K PoinTs generation
Characteristic: NOT INTERNAL
Variable type: integer array ngkpt(3)
Default is No Default
Used when kptopt>=0,
if kptrlatt
has not been defined (kptrlatt
and ngkpt are exclusive of each other).
Its three positive components
give the number of k points of Monkhorst-Pack grids
(defined with respect to primitive axis in reciprocal space)
in each of the three dimensions.
ngkpt will be used to generate the
corresponding kptrlatt
input variable.
The use of nshiftk
and shiftk, allows to generate
shifted grids, or Monkhorst-Pack grids defined
with respect to conventional unit cells.
When nshiftk=1,
kptrlatt is initialized
as a diagonal (3x3) matrix, whose diagonal elements
are the three values ngkpt(1:3). When
nshiftk is greater than 1,
ABINIT will try to generate kptrlatt
on the basis of the primitive vectors of the k-lattice:
the number of shifts might be reduced, in which case
kptrlatt will not be diagonal
anymore.
Monkhorst-Pack grids are usually the most efficient when
their defining integer numbers are even.
For a measure of the efficiency, see the input variable
kptrlen.
Go to the top
| Complete list of input variables
nkpt
Mnemonics: Number of K - Points
Characteristic:
Variable type: integer parameter
Default is 0 if kptopt/=0, and 1 if kptopt==0.
If non-zero,
nkpt
gives the number of k points in the k point array
kpt. These points
are used either to sample the Brillouin zone, or to
build a band structure along specified lines.
If nkpt is zero, the code deduces from other input variables
(see the list in the description of kptopt)
the number of k points, which is possible only
when kptopt/=0.
If kptopt/=0 and
the input value of nkpt/=0,
then ABINIT will check that the number of k points
generated from the other input variables
is exactly the same than nkpt.
If kptopt is positive,
nkpt must be coherent with the values
of kptrlatt,
nshiftk
and shiftk.
For ground state calculations, one should select the
k point in the irreducible Brillouin Zone (obtained
by taking into account point symmetries and the time-reversal
symmetry).
For response function calculations, one should
select k points in the full Brillouin zone, if the wavevector
of the perturbation does not vanish, or in a half of
the Brillouin Zone if q=0. The code will automatically decrease
the number of k points to the minimal set needed for
each particular perturbation.
If kptopt is negative,
nkpt will be the sum of the number of points on
the different lines of the band structure.
For example,
if kptopt=-3, one
will have three segments; supposing
ndivk is 10 12 17,
the total number of k points of the circuit will be
10+12+17+1(for the final point)=40.
Go to the top
| Complete list of input variables
nshiftk
Mnemonics: Number of SHIFTs for K point grids
Characteristic:
Variable type: integer parameter
Default is 1.
This parameter
gives the number of shifted grids
to be used concurrently to generate the full grid of k points.
It can be used with primitive grids defined either from
ngkpt
or
kptrlatt.
The maximum allowed value of nshiftk is 8.
The values of the shifts are given by shiftk.
Go to the top
| Complete list of input variables
nsppol
Mnemonics: Number of SPin POLarization
Characteristic:
Variable type: integer parameter
Default is 1.
Give the number of INDEPENDENT
spin polarisations. Can take the values
1 or 2.
If nsppol=1, one has an unpolarized calculation
(nspinor=1,
nspden=1) or
an antiferromagnetic system
(nspinor=1,
nspden=2), or
a calculation in which spin up and spin down cannot be disantengled
(nspinor=2), that is, either
non-collinear magnetism or presence of spin-orbit coupling,
for which one needs spinor wavefunctions.
If nsppol=2, one has a spin-polarized (collinear) calculation
with separate and different wavefunctions for up and
down spin electrons for each band and k point.
Compatible only with nspinor=1,
nspden=2.
In the present status of development,
with nsppol=1,
all values of ixc are allowed, while
with nsppol=2,
some values of ixc might not be allowed (e.g. 2, 3, 4, 5, 6, 20, 21, 22 are not allowed).
See also the input variable nspden
for the components of the density matrix with respect to
the spin-polarization.
Go to the top
| Complete list of input variables
nstep
Mnemonics: Number of (non-)self-consistent field STEPS
Characteristic:
Variable type: integer parameter
Default is 30. (was 1 before v5.3)
Gives the maximum number of cycles (or "iterations") in a SCF or non-SCF run.
Full convergence from random numbers if usually achieved in
12-20 SCF iterations. Each can take from minutes to hours.
In certain difficult cases, usually related to a small or
zero bandgap or magnetism, convergence performance may be much worse.
When the convergence tolerance tolwfr on the wavefunctions
is satisfied, iterations will stop, so for well converged
calculations you should set nstep to a value larger than
you think will be needed for full convergence, e.g.
if 20 steps usually converges the system, set nstep to 30.
For non-self-consistent runs (iscf < 0) nstep governs
the number of cycles of convergence for the wavefunctions for a fixed density
and Hamiltonian.
NOTE that a choice of nstep=0 is permitted; this will
either read wavefunctions from disk (with irdwfk=1
or irdwfq=1,
or non-zero getwfk
or getwfq in the case
of multi-dataset) and
compute the density, the total energy and stop, or else
(with all of the above vanishing) will initialize
randomly the wavefunctions and
compute the resulting density and total energy.
This is provided for testing purposes.
Also NOTE that nstep=0
with irdwfk=1 will exactly give the same result as
the previous run only if the latter is done with iscf<10
(potential mixing).
One can output the density by using prtden.
The forces and stress tensor are computed with nstep=0.
Go to the top
| Complete list of input variables
nsym
Mnemonics: Number of SYMmetry operations
Characteristic: SYMMETRY FINDER
Variable type: integer parameter
Default is 0.
Gives number of space group symmetries
to be applied in this problem. Symmetries will be input in
array "symrel" and (nonsymmorphic) translations vectors
will be input
in array "tnons". If there is no symmetry in the problem
then set nsym to 1, because the identity is still a symmetry.
In case of a RF calculation, the code is able to use
the symmetries of the system to decrease the number of
perturbations to be calculated, and to decrease of the
number of special k points to be used for the sampling of
the Brillouin zone.
After the response to the perturbations have been calculated,
the symmetries are used to generate as many as
possible elements of the 2DTE from those already
computed.
SYMMETRY FINDER mode (Default mode).
If nsym is 0, all the atomic coordinates must be
explicitely given (one cannot use the geometry builder
and the symmetrizer): the code will then find automatically
the symmetry operations that leave the lattice and each
atomic sublattice invariant. It also checks whether the
cell is primitive (see chkprim).
Note that the tolerance on symmetric atomic positions and
lattice is rather stringent :
for a symmetry operation to be admitted,
the lattice and atomic positions must map on themselves
within 1.0e-8 .
The user is allowed to set up systems with non-primitive unit cells (i.e.
conventional FCC or BCC cells, or supercells without any distortion).
In this case, pure translations will be identified as symmetries
of the system by the symmetry finder.
Then, the combined "pure translation + usual rotation and inversion" symmetry
operations can be very numerous. For example, a conventional FCC cell
has 192 symmetry operations, instead of the 48 ones of the primitive cell.
A maximum limit of 384 symmetry operations is hard-coded. This
corresponds to the maximum number of symmetry operations of a 2x2x2
undistorted supercell. Going beyond
that number will make the code stop very rapidly. If you want
nevertheless, for testing purposes, to treat a larger number of symmetries,
change the initialization of "msym" in the abinit.F90 main routine,
then recompile the code.
For GW calculation, the user might want to select only the symmetry operations whose
non-symmorphic translation vector tnons
is zero. This can be done with the help of the input variable
symmorphi
Go to the top
| Complete list of input variables
ntypat
Mnemonics: Number of TYPEs of atoms
Characteristic: NO MULTI
Variable type: integer parameter
Default is 1.
Gives the number of types of atoms. E.g. for
a homopolar system (e.g. pure Si) ntypat is 1, while for BaTiO3,
ntypat is 3.
Except when alchemical mixing of pseudopotentials is used, the number
of types of atoms will be equal to the number of pseudopotentials
npsp to be provided by the user.
Thus, the code will try to read the same number of pseudopotential files,
whose names should have been given in the "files" file.
The first pseudopotential will be assigned the type number 1, and so
on ...
Go to the top
| Complete list of input variables
occopt
Mnemonics: OCCupation OPTion
Characteristic:
Variable type: integer option parameter
Default is occopt=1
Controls how input
parameters nband, occ,
and wtk are handled.
- occopt=0:
All k points have the same number of bands
and the same occupancies of bands. nband is given as a
single number, and occ(nband)
is an array of nband
elements, read in by the code.
The k point weights in array wtk(nkpt) are
automatically normalized by the code to add to 1.
- occopt=1:
Same as occopt=0, except that the array occ is
automatically generated by the code, to give a semiconductor.
An error occurs when filling cannot be done with
occupation numbers equal to 2 or 0 in each k-point (non-spin-polarized case),
or with occupation numbers equal to 1 or 0 in each k-point (spin-polarized case).
- occopt=2:
k points may optionally have different numbers of
bands and different occupancies. nband(
nkpt*nsppol) is given
explicitly as an array of nkpt*nsppol elements.
occ() is given explicitly for all bands at each k point,
and eventually for each spin --
the total number of elements is the sum of nband(ikpt)
over all k points and spins. The k point weights wtk
(nkpt) are
NOT automatically normalized under this option.
- occopt=3, 4, 5, 6 and 7
Metallic occupation of levels, using different occupation
schemes (see below). The corresponding thermal
broadening, or cold smearing, is defined by
the input variable tsmear (see below : the variable
xx is the energy in Ha, divided by tsmear)
Like for occopt=1, the variable occ is not read
All k points have the same number of bands,
nband is given as a single number, read by the code.
The k point weights in array wtk(nkpt) are
automatically normalized by the code to add to 1.
- occopt=3:
Fermi-Dirac smearing (finite-temperature metal)
Smeared delta function : 0.25d0/(cosh(xx/2.0d0)**2)
- occopt=4:
"Cold smearing" of N. Marzari (see his thesis work),
with a=-.5634 (minimization of the bump)
Smeared delta function :
exp(-xx^{2})/sqrt(pi) * (1.5d0+xx*(-a*1.5d0+xx*(-1.0d0+a*xx)))
- occopt=5:
"Cold smearing" of N. Marzari (see his thesis work),
with a=-.8165 (monotonic function in the tail)
Same smeared delta function as occopt=4, with different a.
- occopt=6:
Smearing of Methfessel and Paxton (PRB40,3616(1989))
with Hermite polynomial of degree 2, corresponding
to "Cold smearing" of N. Marzari with a=0
(so, same smeared delta function as occopt=4, with different a).
- occopt=7:
Gaussian smearing, corresponding to the 0 order
Hermite polynomial of Methfessel and Paxton.
Smeared delta function : 1.0d0*exp(-xx**2)/sqrt(pi)
- occopt=8:
Uniform smearing (the delta function is replaced by a constant function of value one
over ]-1/2,1/2[ (with one-half value at the boundaries). Used for testing purposes only.
WARNING : one can use metallic occupation of levels in the
case of a molecule, in order to avoid any problem with
degenerate levels. However, it is advised NOT to use
occopt=6 (and to a lesser extent occopt=4 and 5),
since the associated number of electron
versus the Fermi energy is NOT guaranteed to be
a monotonic function. For true metals, AND a sufficiently
dense sampling of the Brillouin zone, this should not happen,
but be cautious ! As an indication of this problem,
a small variation of input parameters might lead to
a jump of total energy, because there might be two or even
three possible values of the Fermi energy, and the
bisection algorithm find one or the other.
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rprim
Mnemonics: Real space PRIMitive translations
Characteristic: EVOLVING (if ionmov==2 and optcell/=0)
Variable type: real array rprim(3,3), represented internally as rprim(3,3,nimage)
Default is 3x3 unity matrix.
Give, in columnwise entry,
the three dimensionless primitive translations in real space, to be rescaled by
acell and scalecart.
If the Default is used, that is, rprim is the unity matrix,
the three dimensionless primitive vectors are three
unit vectors in cartesian coordinates. Each will be (possibly) multiplied
by the corresponding acell value, then (possibly)
stretched along the cartesian coordinates by the corresponding scalecart value,
to give the dimensional primitive vectors, called rprimd.
In the general case, the dimensional cartesian
coordinates of the crystal primitive translations R1p, R2p and R3p, see
rprimd, are
where i=1,2,3 is the component of the primitive translation (i.e. x, y, and z).
The rprim variable, scaled by scalecart, is thus used to define directions
of the primitive vectors, that will be multiplied (so keeping the direction unchanged) by
the appropriate length scale acell(1), acell(2),
or acell(3),
respectively to give the dimensional primitive translations
in real space in cartesian coordinates.
Presently, it is requested that the mixed product
(R1xR2).R3 is positive. If this is not the case,
simply exchange a pair of vectors.
To be more specific, keeping the default value of scalecart=1 to simplify the matter,
rprim 1 2 3 4 5 6 7 8 9 corresponds to input of the
three primitive translations R1=(1,2,3) (to be multiplied by acell(1)), R2=(4,5,6) (to be multiplied by acell(2)), and R3=(7,8,9) (to be multiplied by acell(3)).
Note carefully that the first
three numbers input are the first column of rprim, the next
three are the second, and the final three are the third.
This corresponds with the usual Fortran order for arrays.
The matrix whose columns are the reciprocal space primitive
translations is the inverse transpose of the matrix whose
columns are the direct space primitive translations.
Alternatively to rprim, directions of dimensionless primitive
vectors can be specified by using the input variable angdeg.
This is especially useful for hexagonal lattices (with 120 or 60 degrees angles).
Indeed, in order for symmetries to be recognized, rprim must be symmetric up to
tolsym (10 digits by default),
inducing a specification such as
rprim 0.86602540378 0.5 0.0
-0.86602540378 0.5 0.0
0.0 0.0 1.0
that can be avoided thanks to angdeg:
angdeg 90 90 120
Although the use of scalecart or acell is
rather equivalent when the primitive vectors are aligned with the cartesian directions, it is not the case for
non-orthogonal primitive vectors. In particular, beginners often make the error of trying to use acell
to define primitive vectors in face-centered tetragonal lattice, or body-centered tetragonal lattice, or similarly
in face or body-centered orthorhombic lattices. Let's take the example of a body-centered tetragonal lattice, that
might be defined using the following ("a" and "c" have to be replaced by the appropriate conventional cell vector length):
rprim "a" 0 0
0 "a" 0
"a/2" "a/2" "c/2"
acell 3*1 scalecart 3*1 ! ( These are default values)
The following is a valid, alternative way to define the same primitive vectors :
rprim 1 0 0
0 1 0
1/2 1/2 1/2
scalecart "a" "a" "c"
acell 3*1 ! ( These are default values)
Indeed, the cell has been stretched along the cartesian coordinates, by "a", "a" and "c" factors.
At variance, the following is WRONG :
rprim 1 0 0
0 1 0
1/2 1/2 1/2
acell "a" "a" "c" ! THIS IS WRONG
scalecart 3*1 ! ( These are default values)
Indeed, the latter would correspond to :
rprim "a" 0 0
0 "a" 0
"c/2" "c/2" "c/2"
acell 3*1 scalecart 3*1 ! ( These are default values)
Namely, the third vector has been rescaled by "c". It is not at all in the center of the tetragonal cell whose basis vectors
are defined by the scaling factor "a".
As another difference between scalecart or acell,
note that scalecart is NOT INTERNAL :
its content will be immediately applied to rprim, at parsing time,
and then scalecart will be set to the default values (3*1). So, in case scalecart is used,
the echo of rprim in the output file is not the value contained in the input file,
but the value rescaled by scalecart.
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rprimd
Mnemonics: Real space PRIMitive translations, Dimensional
Characteristic: INTERNAL, EVOVING(if ionmov==2 and optcell/=0)
Variable type: real array rprimd(3,3), represented internally as rprimd(3,3,nimage)
This internal variable gives the dimensional real space primitive
vectors, computed from acell,
scalecart,
and rprim.
- R1p(i)=rprimd(i,1)=scalecart(i)*rprim(i,1)*acell(1) for i=1,2,3 (x,y,and z)
- R2p(i)=rprimd(i,2)=scalecart(i)*rprim(i,2)*acell(2) for i=1,2,3
- R3p(i)=rprimd(i,3)=scalecart(i)*rprim(i,3)*acell(3) for i=1,2,3
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scalecart
Mnemonics: SCALE CARTesian coordinates
Characteristic: NOT INTERNAL
Variable type: real array scalecart(3)
Default is 3*1
Gives the scaling factors of cartesian coordinates by which
dimensionless primitive translations (in "rprim") are
to be multiplied.
rprim input variable,
the acell input variable,
and the associated internal rprimd internal variable.
Especially useful for body-centered and face-centered tetragonal lattices, as well as
body-centered and face-centered orthorhombic lattices, see rprimd.
Note that this input variable is NOT INTERNAL : its content will be immediately applied to rprim, at parsing time,
and then scalecart will be set to the default values. So, it will not be echoed.
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shiftk
Mnemonics: SHIFT for K points
Characteristic:
Variable type: real array shift(3,nshiftk)
Default is 0.5 0.5 0.5 ... 0.5
It is used only when kptopt>=0,
and must be defined if nshiftk is larger than 1.
shiftk(1:3,1:nshiftk) defines
nshiftk shifts
of the homogeneous grid of k points
based on ngkpt or
kptrlatt.
The shifts induced by shiftk corresponds
to the reduced coordinates in the coordinate system
defining the k-point lattice. For example,
if the k point lattice is defined using ngkpt,
the point whose reciprocal space reduced coordinates are
( shiftk(1,ii)/ngkpt(1)
shiftk(2,ii)/ngkpt(2)
shiftk(3,ii)/ngkpt(3) )
belongs to the shifted grid number ii.
The user might rely on ABINIT to suggest suitable and
efficient combinations of kptrlatt
and shiftk.
The procedure to be followed is described with the
input variables kptrlen.
In what follows, we suggest some interesting values of the shifts,
to be used with even values of ngkpt.
This list is much less exhaustive than the above-mentioned automatic
procedure.
1) When the primitive vectors of the lattice do NOT form
a FCC or a BCC lattice, the usual (shifted) Monkhorst-Pack
grids are formed by using
nshiftk=1 and shiftk 0.5 0.5 0.5 .
This is often the preferred k point sampling.
For a non-shifted Monkhorst-Pack grid, use
nshiftk=1 and shiftk 0.0 0.0 0.0 ,
but there is little reason to do that.
2) When the primitive vectors of the lattice form a FCC lattice,
with rprim
0.0 0.5 0.5
0.5 0.0 0.5
0.5 0.5 0.0
the (very efficient) usual Monkhorst-Pack sampling will be generated by using
nshiftk= 4 and shiftk
0.5 0.5 0.5
0.5 0.0 0.0
0.0 0.5 0.0
0.0 0.0 0.5
3) When the primitive vectors of the lattice form a BCC lattice,
with rprim
-0.5 0.5 0.5
0.5 -0.5 0.5
0.5 0.5 -0.5
the usual Monkhorst-Pack sampling will be generated by using
nshiftk= 2 and shiftk
0.25 0.25 0.25
-0.25 -0.25 -0.25
However, the simple sampling
nshiftk=1 and shiftk 0.5 0.5 0.5
is excellent.
4) For hexagonal lattices with hexagonal axes, e.g. rprim
1.0 0.0 0.0
-0.5 sqrt(3)/2 0.0
0.0 0.0 1.0
one can use
nshiftk= 1 and shiftk 0.0 0.0 0.5
In rhombohedral axes, e.g. using angdeg 3*60.,
this corresponds to shiftk 0.5 0.5 0.5, to keep the shift along the
symmetry axis.
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symrel
Mnemonics: SYMmetry in REaL space
Characteristic:
Variable type: integer array symrel(3,3,nsym)
Default is the identity matrix for one symmetry.
Gives "nsym" 3x3 matrices
expressing space group symmetries in terms of their action
on the direct (or real) space primitive translations.
It turns out that these can always be expressed as integers.
Always give the identity matrix even if no other symmetries
hold, e.g.
symrel 1 0 0 0 1 0 0 0 1
Also note that for this array as for all others the array
elements are filled in a columnwise order as is usual for
Fortran.
The relation between the above symmetry matrices symrel,
expressed in the basis of primitive translations, and
the same symmetry matrices expressed in cartesian coordinates,
is as follows. Denote the matrix whose columns are the
primitive translations as R, and denote the cartesian
symmetry matrix as S. Then
symrel = R(inverse) * S * R
where matrix multiplication is implied.
When the symmetry finder is used (see nsym), symrel
will be computed automatically.
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tnons
Mnemonics: Translation NON-Symmorphic vectors
Characteristic:
Variable type: real array tnons(3,nsym)
Gives the (nonsymmorphic) translation
vectors associated with the symmetries expressed
in "symrel".
These may all be 0, or may be fractional (nonprimitive)
translations expressed relative to the real space
primitive translations (so, using the "reduced" system
of coordinates, see "xred").
If all elements of the space
group leave 0 0 0 invariant, then these are all 0.
When the symmetry finder is used (see nsym), tnons
is computed automatically.
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toldfe
Mnemonics: TOLerance on the DiFference of total Energy
Characteristic: ENERGY
Variable type: real parameter
Default is 0.0 (stopping condition ignored)
Sets a tolerance for absolute differences
of total energy that, reached TWICE successively,
will cause one SCF cycle to stop (and ions to be moved).
Can be specified in Ha (the default), Ry, eV or Kelvin, since
toldfe has the
'ENERGY' characteristics.
(1 Ha=27.2113845 eV)
If set to zero, this stopping condition is ignored.
Effective only when SCF cycles are done (iscf>0).
Because of machine precision, it is not worth to try
to obtain differences in energy that are smaller
than about 1.0d-12 of the total energy.
To get accurate stresses may be quite demanding.
When the geometry is optimized (relaxation of atomic positions or primitive vectors), the use of
toldfe is to be avoided. The use of toldff or
tolrff is by far preferable, in order to have a handle on the
geometry characteristics. When all forces vanish by symmetry (e.g. optimization of the lattice parameters
of a high-symmetry crystal), then place toldfe to 1.0d-12, or use (better) tolvrs.
Since toldfe, toldff,
tolrff,
tolvrs and tolwfr
are aimed at the same goal (causing the SCF cycle to stop),
they are seen as a unique input variable at reading. Hence, it is forbidden that two of these input variables
have non-zero values for the same dataset, or generically (for all datasets).
However, a non-zero value for one such variable for one dataset will have precedence on the non-zero value for another
input variable defined generically.
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| Complete list of input variables
toldff
Mnemonics: TOLerance on the DiFference of Forces
Characteristic:
Variable type: real parameter
Default is 0.0 (stopping condition ignored)
Sets a tolerance for differences of forces
(in hartree/Bohr) that, reached TWICE successively,
will cause one SCF cycle to stop (and ions to be moved).
If set to zero, this stopping condition is ignored.
Effective only when SCF cycles are done (iscf>0).
This tolerance applies to any particular cartesian
component of any atom, INCLUDING fixed ones.
This is to be used when trying to equilibrate a
structure to its lowest energy configuration (ionmov=2),
or in case of molecular dynamics (ionmov=1)
A value ten times smaller
than tolmxf is suggested (for example 5.0d-6 hartree/Bohr).
This stopping criterion is not allowed for RF calculations.
Since toldfe, toldff,
tolrff,
tolvrs and tolwfr
are aimed at the same goal (causing the SCF cycle to stop),
they are seen as a unique input variable at reading. Hence, it is forbidden that two of these input variables
have non-zero values for the same dataset, or generically (for all datasets).
However, a non-zero value for one such variable for one dataset will have precedence on the non-zero value for another
input variable defined generically.
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| Complete list of input variables
tolrff
Mnemonics: TOLerance on the Relative diFference of Forces
Characteristic:
Variable type: real parameter
Default is 0.0 (stopping condition ignored)
Sets a tolerance for the ratio of differences of forces
(in hartree/Bohr) to maximum force, that, reached TWICE successively,
will cause one SCF cycle to stop (and ions to be moved) : diffor < tolrff * maxfor.
If set to zero, this stopping condition is ignored.
Effective only when SCF cycles are done (iscf>0).
This tolerance applies to any particular cartesian
component of any atom, INCLUDING fixed ones.
This is to be used when trying to equilibrate a
structure to its lowest energy configuration (ionmov=2),
or in case of molecular dynamics (ionmov=1)
A value of 0.02 is suggested.
This stopping criterion is not allowed for RF calculations.
Since toldfe, toldff,
tolrff,
tolvrs and tolwfr
are aimed at the same goal (causing the SCF cycle to stop),
they are seen as a unique input variable at reading. Hence, it is forbidden that two of these input variables
have non-zero values for the same dataset, or generically (for all datasets).
However, a non-zero value for one such variable for one dataset will have precedence on the non-zero value for another
input variable defined generically.
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| Complete list of input variables
tolvrs
Mnemonics: TOLerance on the potential V(r) ReSidual
Characteristic:
Variable type: real parameter
Default is 0.0 (stopping condition ignored)
Sets a tolerance for potential
residual that, when reached, will cause one SCF cycle
to stop (and ions to be moved).
If set to zero, this stopping condition is ignored.
Effective only when SCF cycles are done (iscf>0).
To get accurate stresses may be quite demanding.
Additional explanation : the residual of the potential is the difference between the
input potential and the output potential, when the latter is obtained from the density
determined from the eigenfunctions of the input potential. When the self-consistency
loop is achieved, both input and output potentials must be equal, and the residual
of the potential must be zero. The tolerance on the
potential residual is imposed by first subtracting the mean of the residual of the potential
(or the trace of the potential matrix, if the system is spin-polarized),
then summing the square of this function over all FFT grid points. The result should be
lower than tolvrs.
Since toldfe, toldff,
tolrff,
tolvrs and tolwfr
are aimed at the same goal (causing the SCF cycle to stop),
they are seen as a unique input variable at reading. Hence, it is forbidden that two of these input variables
have non-zero values for the same dataset, or generically (for all datasets).
However, a non-zero value for one such variable for one dataset will have precedence on the non-zero value for another
input variable defined generically.
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| Complete list of input variables
tolwfr
Mnemonics: TOLerance on WaveFunction squared Residual
Characteristic:
Variable type: real parameter
Default is 0.0d0 (stopping criterion ignored)
The signification of this tolerance depends on
the basis set. In plane waves, it gives a convergence tolerance for the
largest squared "residual" (defined below) for any
given band. The squared residual is:
< nk|(H-E)^{2}|nk >, E = < nk|H|nk >
which clearly is nonnegative and goes to 0 as
the iterations converge to an eigenstate.
With the squared residual expressed in
Hartrees^{2} (Hartrees squared), the largest squared
residual (called residm) encountered over all bands
and k points must be less than tolwfr for iterations
to halt due to successful convergence.
Note that if iscf>0, this criterion should be replaced
by those based on toldfe (preferred for ionmov==0),
toldff
tolrff (preferred for ionmov/=0), or
tolvrs (preferred for theoretical reasons!).
When tolwfr is 0.0, this criterion is ignored,
and a finite value of toldfe, toldff
or tolvrs must be specified.
This also imposes a restriction
on taking an ion step; ion steps are not permitted
unless the largest squared residual is less than
tolwfr, ensuring accurate forces.
To get accurate stresses may be quite demanding.
Note that the preparatory GS calculations
before a RF calculations must be highly converged.
Typical values for these preparatory runs are tolwfr
between 1.0d-16 and 1.0d-22.
Note that tolwfr is often used in the test cases, but this is
tolwfr purely for historical reasons :
except when iscf<0, other critera
should be used.
In the wavelet case (see usewvl =
1), this criterion is the favoured one. It is based on the
norm 2 of the gradient of the wavefunctions. Typical values
range from 5*10^{-4} to 5*10^{-5}.
Since toldfe, toldff,
tolrff,
tolvrs and tolwfr
are aimed at the same goal (causing the SCF cycle to stop),
they are seen as a unique input variable at reading. Hence, it is forbidden that two of these input variables
have non-zero values for the same dataset, or generically (for all datasets).
However, a non-zero value for one such variable for one dataset will have precedence on the non-zero value for another
input variable defined generically.
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typat
Mnemonics: TYPE of atoms
Characteristic:
Variable type: integer array typat(natom) (or : typat(natrd), if the geometry builder is used)
Default is 1 (for natom=1)
Array giving an integer label to every atom in the unit
cell to denote its type.
The different types of atoms
are constructed from the pseudopotential files.
There are at most ntypat types of atoms.
As an example, for BaTiO3, where the pseudopotential for Ba is number 1,
the one of Ti is number 2, and the one of O is number 3, the actual
value of the typat array might be :
typat 1 2 3 3 3
The array typat has to agree with the actual locations
of atoms given in xred , xcart or
xangst, and the input
of pseudopotentials has to be ordered to agree with the
atoms identified in typat.
The nuclear charge of the
elements, given by the array znucl, also must agree with
the type of atoms designated in "typat".
The array typat is
not constrained to be increasing. An
internal representation of the list of atoms,
deep in the code (array atindx), groups the atoms of same type
together. This should be transparent to the
user, while keeping efficiency.
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udtset
Mnemonics: Upper limit on DaTa SETs
Characteristic:
Variable type: integer array udtset(2)
Default is No Default (since it is not used when it is not defined).
Used to define the set of indices in the multi-data set
mode, when a double loop is needed (see later).
The values of udtset(1) must be between 1 and 999,
the values of udtset(2) must be between 1 and 9, and their
product must be equal to ndtset.
The values of jdtset are obtained by
looping on the two indices defined by udtset(1) and udtset(2) as follows :
do i1=1,intarr(1)
do i2=1,intarr(2)
idtset=idtset+1
dtsets(idtset)%jdtset=i1*10+i2
end do
end do
So, udtset(2) sets the largest value for the unity digit, that varies between 1 and udtset(2).
If udtset is used, the input variable jdtset cannot be used.
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usewvl
Mnemonics: Use WaVeLet basis set
Characteristic:
Variable type: integer (0 or 1)
Default is 0 (use plane-wave basis set).
Used to define if the calculation is done on a
wavelet basis set or not.
The values of usewvl must be 0 or 1. Putting usewvl
to 1, makes icoulomb
mandatory to 1. The number of band (nband) must be set manually to
the strict number need for an isolator system (i.e.
number of electron over two). The cut-off is not relevant in the
wavelet case, use wvl_hgrid
instead.
In wavelet case, the system must be isolated systems (molecules or
clusters). All geometry optimization are available (see ionmov, especially the geometry
optimisation and the molecular dynamics.
The spin computation is not currently possible with wavelets and
metalic systems may be slow to converge.
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wtk
Mnemonics: WeighTs for K points
Characteristic:
Variable type: real array wtk(nkpt)
Default is nkpt*1.0d0 except when kptopt/=0.
Gives the k point weights.
The
k point weights will have their sum (re)normalized to 1
(unless occopt=2 and kptopt=0;
see description of occopt)
within the program and therefore may be input with any
arbitrary normalization. This feature helps avoid the
need for many digits in representing fractional weights
such as 1/3.
wtk is ignored if iscf is not positive,
except if iscf=-3.
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wvl_hgrid
Mnemonics: WaVeLet H step GRID
Characteristic: LENGTH
Variable type: real parameter
Default is 0.5d0 .
It gives the step size in real space for the
grid resolution in the wavelet basis set. This value is highly
responsible for the memory occupation in the wavelet
computation. The value is a length in atomic units.
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xangst
Mnemonics: vectors (X) of atom positions in cartesian coordinates -length in ANGSTrom-
Characteristic: NOT INTERNAL
Variable type: real array xangst(3,natom) (or xangst(3,natrd) if the geometry builder is used)
Gives the cartesian coordinates
of atoms within unit cell, in angstrom. This information is
redundant with that supplied by array xred or xcart.
If xred and xangst are ABSENT from the input file and
xcart is
provided, then the values of xred will be computed from
the provided xcart (i.e. the user may use xangst instead
of xred or xcart to provide starting coordinates).
One and only one of xred, xcart
and xangst must be provided.
The conversion factor between Bohr and Angstrom
is 1 Bohr=0.5291772108 Angstrom, see the NIST site.
Atomic positions evolve if ionmov/=0 .
In constrast with xred and
xcart, xangst is not internal.
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xcart
Mnemonics: vectors (X) of atom positions in CARTesian coordinates
Characteristic: EVOLVING, LENGTH
Variable type: real array xcart(3,natom) (or xcart(3,natrd) if the geometry builder is used)
Gives the cartesian coordinates
of atoms within unit cell. This information is
redundant with that supplied by array xred or xangst.
By default, xcart is given in Bohr atomic units
(1 Bohr=0.5291772108 Angstroms), although Angstrom can be specified,
if preferred, since xcart has the
'LENGTH' characteristics.
If xred and xangst are
ABSENT from the input file and xcart is
provided, then the values of xred will be computed from
the provided xcart (i.e. the user may use xcart instead
of xred or xangst to provide starting coordinates).
One and only one of xred, xcart
and xangst must be provided.
Atomic positions evolve if ionmov/=0 .
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xred
Mnemonics: vectors (X) of atom positions in REDuced coordinates
Characteristic: EVOLVING
Variable type: real array xred(3,natom) (or xred(3,natrd) if the geometry builder is used), represented internally as xred(3,natom,nimage)
Default is all 0.0d0
Gives the atomic locations within
unit cell in coordinates relative to real space primitive
translations (NOT in cartesian coordinates). Thus these
are fractional numbers typically between 0 and 1 and
are dimensionless. The cartesian coordinates of atoms (in Bohr)
are given by:
R_cartesian = xred1*rprimd1+xred2*rprimd2+xred3*rprimd3
where (t1,t2,t3) are the "reduced coordinates" given in
columns of "xred", (rprimd1,rprimd2,rprimd3) are the columns of
primitive vectors array "rprimd" in Bohr.
If you prefer to work only with cartesian coordinates, you
may work entirely with "xcart" or "xangst" and ignore xred, in
which case xred must be absent from the input file.
One and only one of xred, xcart
and xangst must be provided.
Atomic positions evolve if ionmov/=0 .
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| Complete list of input variables
znucl
Mnemonics: charge -Z- of the NUCLeus
Characteristic: NO MULTI
Variable type: real array znucl(npsp)
Gives nuclear charge for each
type of pseudopotential, in order.
If znucl does not agree with nuclear charge,
as given in pseudopotential files, the program writes
an error message and stops.
N.B. : In the pseudopotential files, znucl is called "zatom".
For a "dummy" atom, with znucl=0 , as used in the case of calculations
with only a jellium surface, ABINIT sets arbitrarily the covalent radius to one.
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| Complete list of input variables