ABINIT, groundstate calculation variables:
List and description.
This document lists and provides the description
of the name (keywords) of all files handling input
variables to be used in the main input file of the abinis 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 responsefunction calculations using
abinis, the complementary file ~ABINIT/Infos/respfn_help is needed.
Copyright (C) 19982004 ABINIT group (DCA, XG, RC)
This file is distributed under the terms of the GNU General Public License, see
~ABINIT/Infos/copyright or
http://www.gnu.org/copyleft/gpl.txt .
For the initials of contributors, see ~ABINIT/Infos/contributors .
Goto :
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List of input variables

Tutorial home page

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Help files :
New user's guide

Abinis (main)

Abinis (respfn)

Mrgddb

Anaddb

AIM (Bader)

Cut3D
Files that describe other input variables:
 Basic variables, VARBAS
 Developper variables, VARDEV
 Geometry builder + symmetry related variables, VARGEO
 GW variables, VARGW
 File handling variables, VARFIL
 Internal variables, VARINT
 Parallelisation variables, VARPAR
 ProjectorAugmented Wave variables, VARPAW
 Response Function variables, VARRF
 Structure optimization variables, VARRLX
Content of the file : alphabetical list of variables.
A.
algalch
B.
bdberry
berryopt
boxcenter
boxcutmin
C.
chkexit
chkprim
cpus, cpum, cpuh
D.
diecut
diegap
dielam
dielng
diemac
diemix
dosdeltae
E.
efield
enunit
F.
fband
fixmom
G.
H.
I.
iatsph
iprcel
J.
K.
kberry
kptbounds
kptrlatt
kptrlen
L.
M.
mixalch
N.
natsph
nberry
nbdbuf
ndivk
ngfft
nline
npsp
%npspalch
nqpt
nspinor
ntypalch
%ntyppure
O.
occ
optdriver
P.
pspso
Q.
qpt
qptnrm
R.
ratsph
S.
so_typat
spinat
stmbias
symafm
T.
timopt
tphysel
tsmear
U.
V.
vacuum
vacwidth
W.
X.
Y.
Z.
algalch
Mnemonics: ALGorithm for generating ALCHemical pseudopotentials
Characteristic:
Variable type: integer array
algalch(ntypalch)
Default is 1 for all indices
Used for the generation of alchemical pseudopotentials, that is,
when ntypalch is nonzero.
Give the algorithm to be used to
generate the ntypalch alchemical potentials
from the different npspalch pseudopotentials
dedicated to this use.
Presently, algalch can only have the value 1, that is :
 the local potentials are mixed, thanks to the mixalch
mixing coefficients
 the form factors of the nonlocal projectors are all preserved, and all considered
to generate the alchemical potential
 the scalar coefficients of the nonlocal projectors are multiplied by the proportion
of the corresponding type of atom that is present in mixalch
 the characteristic radius for the core charge is a
linear combination of the characteristic radii of the core charges,
build with the mixalch mixing
coefficients
 the core charge function f(r/rc) is a linear combination
of the core charge functions, build with the mixalch
mixing coefficients
Later, other algorithms for the mixing might be included.
Go to the top
 Complete list of input variables
bdberry
Mnemonics: BanD limits for BERRY phase
Characteristic:
Variable type: integer array bdberry(4)
Default is 4*0.
Used for nonzero values of berryopt.
Give the lower band and the upper band of the set of bands
for which the Berry phase must be computed.
Irrelevant if nberry is not positive.
When nsppol is 1 (no spinpolarisation),
only the two first numbers, giving the lower and highest
bands, are significant. Their occupation number is assumed to be 2.
When nsppol is 2 (spinpolarized calculation),
the two first numbers give the lowest and highest
bands for spin up, and the third and fourth numbers
give the lowest and highest bands for spin down.
Their occupation number is assumed to be 1 .
Presently, bdband MUST be initialized by the user
in case of Berry phase calculation: the abovementioned
default will cause an early exit.
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 Complete list of input variables
berryopt
Mnemonics: BERRY phase options
Characteristic:
Variable type: integer berryopt
Default is 0
 0 => no computation of expressions relying on a Berry phase (default)
 1 => the computation of Berry phases is activated (berryphase routine)
 2 => the computation of derivatives with respect to the wavevector,
thanks to the Berry phase finitedifference formula, is activated (uderiv routine)
 3 => same as option 1 and 2 together
 4 => finite electric field calculation
 1 => alternative computation of Berry phases (berryphase_new routine)
 2 => alternative computation of derivatives with respect to the wavevector,
thanks to the Berry phase finitedifference formula (berryphase_new routine)
 3 => same as option 1 and 2 together
The other related input variables are :
 in case of berryopt=1,2, or 3 : bdberry
and kberry; also, nberry
must be larger than 0;
 in case of berryopt=1,2, or 3 : the variable
rfdir must be used to specify the primitive
vector along which the projection of the polarization or the ddk will be computed.
For example if berryopt=1 and rfdir=1 0 0,
the projection of the polarization along the reciprocal lattice vector
G_1 is computed. In case rfdir=1 1 1,
ABINIT computes the projection of P along G_1, G_2 and G_3 and transforms the results
to cartesian coordinates;
 efield,
rfdir in case of berryopt=4 ;
The cases berryopt=1,2,3 and 4 work only if
kptopt=3, nsppol=1,
nspinor=1, and
occopt=1.
Go to the top
 Complete list of input variables
boxcenter
Mnemonics: BOX CENTER
Characteristic:
Variable type: real array boxcenter(3)
Default boxcenter(1:3) is 0.5 0.5 0.5 .
Defines the center of the box, in reduced coordinates.
At present, this information is only used in the case of
TimeDependent DFT computation of the oscillator strength.
One must take boxcenter such as to be roughly the center of
the cluster or molecule. The default is sensible when
the vacuum surrounding the cluster or molecule has xred 0 or 1.
On the contrary, when the cluster or molecule is close to
the origin, it is better to take boxcenter=(0 0 0).
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 Complete list of input variables
boxcutmin
Mnemonics: BOX CUToff MINimum
Characteristic:
Variable type: real
Default is 2.0 .
The box cutoff ratio is the ratio between the wavefunction plane wave sphere
radius, and the radius of the sphere that can be inserted in the
FFT box, in reciprocal space. In order for the density to be exact
(in the case of plane wave, not PAW), this ratio should be at least two.
If one uses a smaller ratio, one will gain speed, at the expense of accuracy.
In case of pure ground state calculation (e.g. for the determination
of geometries), this is sensible. However,
the wavefunctions that are obtained CANNOT be used for starting response function
calculation.
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 Complete list of input variables
charge
Mnemonics: CHARGE
Characteristic:
Variable type: real number
Default is 0.
Used to establish charge balance between
the number of electrons filling the bands and the
nominal charge associated with the atomic cores.
The code adds up the number of valence electrons
provided by the pseudopotentials of each type
(call this "zval"), then add charge, to get the
number of electrons per unit cell,
nelect.
Then, if iscf is positive,
the code adds up the band occupancies (given in
array occ) for all bands at each k point,
then multiplies
by the k point weight wtk at each k point.
Call this sum "nelect_occ" (for the number of electrons
from occupation numbers). It is then
required that:
nelect_occ = nelect
To treat a neutral
system, which is desired in nearly all cases, one must
use charge=0. To treat a system missing one electron
per unit cell, set charge=+1.
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 Complete list of input variables
chkexit
Mnemonics: CHecK whether the user want to EXIT
Characteristic:
Variable type: integer parameter
Default is 2 for sequential version of ABINIT,
1 for parallel version of ABINIT.
If chkexit is 1 or 2, ABINIT
will check whether the user wants to interrupt the run (using the keyword
"exit" on the top of the input file or creating a file
named "abinit.exit": see the
end of section 3.2 of abinis_help).
If chkexit=0, the check is not performed at all
If chkexit=1, the check is not performed frequently (after each SCF step)
If chkexit=2, the check is performed frequently
(after a few bands, at each k point)
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 Complete list of input variables
chkprim
Mnemonics: CHecK whether the cell is PRIMitive
Characteristic: SYMMETRY FINDER
Variable type: integer parameter
Default is 1.
If the symmetry finder is used
(see nsym), a nonzero
value of chkprim will make the code stop if a nonprimitive
cell is used. If chkprim=0, a warning is issued, but the run
does not stop.
If you are generating the atomic and cell geometry using
spgroup, you might
generate a PRIMITIVE cell using
brvlatt=1 .
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 Complete list of input variables
cpus, cpum, cpuh
Mnemonics: CPU time limit in: Seconds, Minutes, Hours
Characteristic: NO MULTI ; for cpum and cpuh : NO INTERNAL
Variable type: real parameters
Default is 0.0d0.
One of these three real parameters can be
defined in the input file, to set up a CPU time limit.
When the job reaches that limit, it will try to end smoothly.
However, note that this might still take some time.
If the user want a firm CPU time limit, the present
parameter must be reduced sufficiently. Intuition
about the actual margin to be taken into account
should come with experience ...
Note that only one of these three parameters can be defined
in a single input file.
A zero value has no action of the job.
Internally, only cpus is used in the dtset array: adequate
conversion factors are used to generate it from cpum or
cpuh.
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 Complete list of input variables
diecut
Mnemonics: DIelectric matrix Energy CUToff
Characteristic: DEVELOP, ENERGY
Variable type: real parameter
Default diecut is 2.2d0 Ha.
Kinetic energy cutoff that controls the number
of planewaves used to represent the dielectric matrix:
(1/2)[(2 Pi)*(Gmax)]^{2}=ecut for Gmax.
Can be specified in Ha (the default), Ry, eV or Kelvin, since
ecut has the
'ENERGY' characteristics.
(1 Ha=27.2113961 eV)
All planewaves inside this "basis sphere" centered
at G=0 are included in the basis.
This is useful only when iprcel>=21, which means that
a preconditioning scheme based on the dielectric matrix
is used.
NOTE : a negative diecut will define the same dielectric
basis sphere as the corresponding positive value,
but the FFT grid will be identical to the one used
for the wavefunctions.
The much smaller FFT grid, used when diecut is positive,
gives exactly the same results.
No meaning for RF calculations yet.
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 Complete list of input variables
diegap
Mnemonics: DIelectric matrix GAP
Characteristic: DEVELOP, ENERGY
Variable type: real parameter
Default diegap is 0.1 Ha.
Gives a rough estimation of the dielectric gap
between the highest energy level computed in the run,
and the set of bands not represented.
Used to extrapolate dielectric matrix when iprcel >= 21.
Can be specified in Ha (the default), Ry, eV or Kelvin, since
ecut has the
'ENERGY' characteristics.
(1 Ha=27.2113961 eV)
No meaning for RF calculations yet.
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 Complete list of input variables
dielam
Mnemonics: DIelectric matrix LAMbda
Characteristic: DEVELOP
Variable type: real parameter between 0 and 1
Default dielam is 0.5 .
Gives the amount of occupied states with mean energy given by the
highest level computed in the run, included
in the extrapolation of the dielectric matrix.
Used when iprcel >= 21.
No meaning for RF calculations yet.
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 Complete list of input variables
dielng
Mnemonics: model DIElectric screening LeNGth
Characteristic:
Variable type: real parameter
Default is 1.0774841d0 (bohr), for historical reasons.
Used for screening length (in bohr) of the model
dielectric function, diagonal in reciprocal space.
By default, given in bohr atomic units
(1 bohr=0.5291772083 Angstroms), although Angstrom can be specified,
if preferred, since dielng has the
'LENGTH' characteristics.
This model dielectric function is as follows :
( 1 + dielng^{2} * K^{2} )
diel(K)= 
( 1/diemac + dielng^{2} * K^{2} ) * diemix
The inverse of this model dielectric function will be
applied to the residual, to give the preconditioned
change of potential. Right at K=0, diel(K) is imposed to be 1.
If the preconditioning were perfect,
the change of potential would lead to an exceedingly fast solution
of the selfconsistency problem (two or three steps).
The present model dielectric function is excellent for
rather homogeneous unit cells.
When K>0 , it tends to the macroscopic dielectric
constant, eventually divided by the mixing factor diemix.
For metals, simply put diemac to a very large value (10^6 is OK)
The screening length dielng governs the length scale
to go from the macroscopic regime to the microscopic
regime, where it is known that the dielectric function
should tend to 1. It is on the order of 1 bohr for
metals with medium density of states at the Fermi level,
like Molybdenum, and for Silicon. For metals with a
larger DOS at the Fermi level (like Iron),
the screening will be more effective, so that dielng
has to be decreased by a factor of 24.
This works for GS and RF calculation.
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 Complete list of input variables
diemac
Mnemonics: model DIElectric MACroscopic constant
Characteristic:
Variable type: real parameter
Default is 10^{6} (metallic damping).
A rough knowledge of the macroscopic dielectric constant diemac
of the system is a useful help to speedup the SCF procedure:
a model dielectric function,
see the keyword dielng, is used for that
purpose. It is especially
useful for speeding up the treatment of rather homogeneous unit cells.
Some hint :
The value of diemac should usually be bigger than 1.0d0,
on physical grounds.
For metals, simply put diemac to a very large value (the default 10^{6} is OK)
For silicon, use 12.0 . A similar value is likely to work well for
other semiconductors
For wider gap insulators, use 2.0 ... 4.0
For molecules in an otherwise empty big box, try 1.5 ... 3.0
Systems that combine a highly polarisable part and some vacuum are rather
badly treated by the present version of ABINIT. You have to experiment
a bit to find the best diemac. If you let diemac
to its default value, you might even never obtain the selfconsistent convergence !
For response function calculations, use the same
values as for GS. The improvement in speed can be considerable
for small (but nonzero) values of the wavevector.
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 Complete list of input variables
diemix
Mnemonics: model DIElectric MIXing factor
Characteristic:
Variable type: real parameter
Default is 1.0 .
Gives overall factor of the preconditioned
residual potential to be transferred in the SCF cycle.
It should be between 0.0 and 1.0 .
If the model dielectric function were perfect, diemix
should be 1.0 . By contrast, if the model dielectric function
does nothing (when diemac=1.0d0 or dielng
is larger than the
size of the cell), diemix can be used
to damp the amplifying factor inherent to the SCF loop.
For molecules, a value on the order 0.5 or 0.33 is rather usual.
When iscf=3 or iscf=5, diemix
is only important at the
few first iterations when anharmonic effects are important,
since these schemes compute their own mixing factor
for selfconsistency.
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 Complete list of input variables
dosdeltae
Mnemonics: DOS Delta in Energy
Characteristic: ENERGY
Variable type: real parameter
Default is 0.0 .
Defines the linear grid resolution (energy increment) to be used for the
computation of the DensityOfStates, when prtdos
is nonzero.
If dosdeltae is set to zero (the default value), the actual
increment is 0.001 Ha if prtdos=1, and
the much smaller value 0.00005 Ha if prtdos=2.
This different default value arises because the prtdos=1 case,
based on a smearing technique, gives a quite smooth DOS, while the DOS from the
tetrahedron method, prtdos=2, is rapidly varying.
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 Complete list of input variables
efield
Mnemonics: Electric FIELD
Characteristic:
Variable type: real array efield(3)
Default is 3*0.0 .
In case berryopt=4,
a finite electric field calculation is performed. The value
of this electric field, and its direction is determined by efield.
It must be given in atomic units (1 a.u. of electric field= 514220624373.482 V/m, see note below),
in cartesian coordinates.
References for the calculation under electric field (based on multi k point Berry phase) :
 Nunes and Vanderbilt, PRL 73, 712 (1994) : realspace version of the finitefield Hamiltonian
 Nunes and Gonze, PRB 63, 155197 (2001) : reciprocalspace version of the finitefield Hamiltonian
(the one presently implemented), and extensive theoretical analysis
 Souza, Iniguez and Vanderbilt, PRL 89, 117602 (2003) : implementation of the finitefield Hamiltonian
(reciprocalspace version)
See also Umari, Pasquarello, PRL 90, 027401 (2003).
The atomic unit of electric field strength is :
e_Cb/(4 pi eps0 a0**2), where e_Cb is the electronic charge in Coulomb (1.602176462e19),
eps0 is the electric constant (8.854187817d12 F/m), and a0 is the Bohr radius
in meter (0.5291772083e10).
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 Complete list of input variables
enunit
Mnemonics: ENergy UNITs
Characteristic:
Variable type: integer parameter
Default is 0 (eigenvalues in hartree and phonon frequencies
in hartree and cm1).
Governs the units to be used for
output of eigenvalues (and eventual phonon frequencies)
 0=>print eigenvalues in hartree;
 1=>print eigenvalues in eV;
 2=>print eigenvalues in both hartree and eV.
If phonon frequencies are to computed :
 0=> phonon frequencies in Hartree and cm1;
 1=> phonon frequencies in eV and THz;
 2=> phonon frequencies in hartree, eV, cm1, Thz and Kelvin.
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 Complete list of input variables
fband
Mnemonics: Factor for the number of BANDs
Characteristic: NO INTERNAL
Variable type: real parameter, positive or zero
Default is 0.125 in case occopt==1 (insulating case) and
0.500 for other values of occopt (metallic case). Not used
in case occopt==0 or 2.
Governs the number of bands to be used in the code in the case
the parameter nband is not defined in the input file
(which means that occopt is not equal to 0 or 2).
In case fband is 0.0d0, the code computes from
the pseudopotential files and the geometry data
contained in the input file, the number of electrons
present in the system. Then, it computes the minimum
number of bands that can accomodate them, and use
that value for nband.
In case fband differs from
zero, other bands will be added, just
larger than fband times the number of atoms.
This parameter is not echoed in the top of the main
output file, but only the parameter nband that it allowed
to compute. It is also not present in the dtset array (no internal).
The default values are chosen such as to give naturally some
conduction bands. This improves the robustness of the code,
since this allows to identify lack of convergence coming from
(near)degeneracies at the Fermi level. In the metallic
case, the number of bands generated might be too small
if the smearing factor is large. The occupation numbers
of the higher bands should be small enough such as to
neglect higher bands. It is difficult to automate
this, so a fixed default value has been chosen.
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 Complete list of input variables
fixmom
Mnemonics: FIX the magnetic MOMent
Characteristic:
Variable type: real parameter
Default is 99.99d0
This input variable is active only in the
nsppol=2 case.
If fixmom is not the "magic" value of 99.99d0, the
magnetic moment of the system will be fixed
to the value of fixmom.
Otherwise, the magnetic moment will be determined
selfconsistently, by having the same spin up and spin down
Fermi energy.
Note : for the time being, only the spin down Fermi energy
is written out in the main output file. In the fixed
magnetic moment case, it differs from the
spin up Fermi energy.
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 Complete list of input variables
iatsph
Mnemonics: Index for the ATomic SPHeres of the atomprojected densityofstates
Characteristic:
Variable type: integer array iatsph(1:natsph)
Default is 1, 2, ... natsph
This input variable is active only in the
prtdos=3 case.
It gives the number of the natsph atoms around which the sphere
for atomprojected densityofstates will be build,
in the prtdos=3 case.
The radius of these spheres is given by ratsph.
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 Complete list of input variables
iprcel
Mnemonics: Integer for PReConditioning of ELectron response
Characteristic:
Variable type: integer parameter
Default is 0.
Used when iscf>0, to define the SCF preconditioning scheme.
Potentialbased preconditioning schemes for the SCF loop
(electronic part) are STILL UNDER DEVELOPMENT.
The present parameter (electronic part) describe the way the
change of potential is derived from the residual.
The possible values of iprcel correspond to :
 0 => model dielectric function described by diemac,
dielng
and diemix.
 larger or equal to 21 => will compute the dielectric matrix
according to diecut, dielam,
diegap.
 Between 21 and 29 => for the first few steps
uses the same as option 0 then compute RPA dielectric function,
and use it as such.
 Between 31 and 39 => for the first few steps
uses the same as option 0 then compute RPA dielectric function,
and use it, with the mixing factor diemix.
 Between 41 and 49 => compute the RPA dielectric matrix
at the first step, and recompute it at a later step,
and take into account the mixing factor diemix.
 Between 51 and 59 => same as between 41 and 49, but compute
the RPA dielectric matrix by another mean
 Between 61 and 69 => same as between 41 and 49, but compute
the electronic dielectric matrix instead of the RPA one.
The step at which the dielectric matrix is computed or
recomputed is determined by modulo(iprcel,10).
For nonhomogeneous cells, relatively large, iprcel=45
will likely give a large improvement over iprcel=0.
For nsppol=2 with metallic occopt,
only iprcel=0 is allowed.
No meaning for RF calculations yet.
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 Complete list of input variables
kberry
Mnemonics: K wavevectors for BERRY phase computation
Characteristic:
Variable type: integer array
kberry(3,nberry)
Default is an array of 0
Used for nonzero values of berryopt.
This array defines, for each Berry phase calculation
(the number of such calculations is defined by
nberry), the
difference of wavevector between k points for which
the overlap matrix must be computed.
The polarisation vector will be projected
on the direction of that wavevector,
and the result of the computation will be the magnitude of this
projection.
Doing more than one wavevector, with different independent
direction, allows to find the full polarisation vector.
However, note that converged results need oriented grids,
denser along the difference wavevector than usual MonkhorstPack
grids.
The difference of wavevector is computed in the coordinate
system defined by the kpoints grid
(see ngkpt
and kptrlatt), so that
the values of kberry are integers.
Of course, such a k point grid must exist, and all the
corresponding wavefunctions must be available, so that the
computation is allowed only when kptopt
is equal to 3. In order to save computing time, it is suggested
to make a preliminary calculation of the wavefunctions on the
irreducible part of the grid, with kptopt
equal to 1, and then use these converged wavefunctions
in the entire Brillouin zone, by reading them to initialize
the kptopt=3 computation.
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 Complete list of input variables
kptbounds
Mnemonics: K PoinTs BOUNDarieS
Characteristic: NOT INTERNAL
Variable type: real array
kptbounds(3,abs(kptopt)+1)
No Default
It is used to generate the circuit to be followed by the band structure,
when kptopt is negative (it is
not read if kptopt is zero or positive).
There are abs(kptopt)
segments to be defined, each of which wich start from
the end point of the preceeding one. Thus,
the number of points to be input is
abs(kptopt)+1.
They form a circuit starting
at kptbounds(1:3,1)/kptnrm
and ending at
kptbounds(1:3,abs(kptopt)+1)/kptnrm.
The number of divisions of each segment is defined
by ndivk.
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 Complete list of input variables
kptrlatt
Mnemonics: K  PoinTs grid : Real space LATTice
Characteristic:
Variable type: integer array kptrlatt(3,3)
No default.
This input variable is used only when kptopt
is positive. It partially defines the k point grid.
The other piece of information is contained in
shiftk.
kptrlatt cannot be used together with ngkpt.
The values kptrlatt(1:3,1), kptrlatt(1:3,2), kptrlatt(1:3,3)
are the coordinates of three vectors in real space, expressed
in the rprim coordinate system (reduced coordinates).
They defines a superlattice in real space.
The k point lattice is the reciprocal of this superlattice,
eventually shifted (see shiftk).
If neither ngkpt nor kptrlatt
are defined, ABINIT will automatically generate a set
of k point grids, and select the best combination
of kptrlatt and shiftk
that allows to reach a sufficient value of kptrlen.
See this latter variable for a complete description of this
procedure.
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 Complete list of input variables
kptrlen
Mnemonics: K  PoinTs grid : Real space LENgth
Characteristic:
Variable type: real parameter
Default 20.0d0.
This input variable is used only when kptopt
is positive and nonzero.
Preliminary explanation :
The k point lattice defined by ngkpt
or kptrlatt is used to perform integrations
of periodic quantities in the Brillouin Zone, like
the density or the kinetic energy. One can relate the
error made by replacing the continuous integral by a sum
over k point lattice to the Fourier transform of the
periodic quantity. Erroneous contributions will appear
only for the vectors in real space that belong to the reciprocal
of the k point lattice, except the origin.
Moreover, the expected size of these
contributions usually decreases exponentially with the distance.
So, the length of the smallest of these real space vectors
is a measure of the accuracy of the k point grid.
When either ngkpt or
kptrlatt is defined, kptrlen is not
used as an input variable, but the length of the
smallest vector will be placed in this variable, and echoed
in the output file.
On the other hand, when neither ngkpt nor
kptrlatt are defined, ABINIT will
automatically generate a large set of possible k point grids,
and select among this set, the grids that give
a length of smallest vector LARGER than kptrlen,
and among these grids, the one that, when used with
kptopt=1, reduces to the smallest number
of k points. Note that this procedure can be timeconsuming.
It is worth to do it once for a given unit cell
and set of symmetries, but not use this procedure by default.
The best is then to set prtkpt=1, in order
to get a detailed analysis of the set of grids.
If some layer of vacuum is detected in the unit cell
(see the input variable vacuum), the
computation of kptrlen will ignore the
dimension related to the direction perpendicular
to the vacuum layer, and generate a bidimensional k point grid.
If the system is confined in a tube,
a onedimensional k point grid will be generated.
For a cluster, this procedure will only generate the Gamma point.
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 Complete list of input variables
mixalch
Mnemonics: MIXing coefficients for ALCHemical potentials
Characteristic:
Variable type: integer array
mixalch(npspalch,ntypalch)
Default is 0.d0 (will not accepted !)
Used for the generation of alchemical pseudoatoms, that is,
when ntypalch is nonzero.
This array gives, for each type of alchemical pseudatom (there are
ntypalch such pseudoatoms), the mixing coefficients
of the basic npspalch pseudopotentials for
alchemical use. For each type of alchemical pseudoatom, the sum of the
mixing coefficients must equal 1.
The actual use of the mixing coefficients is defined by the input
variable algalch.
Example 1. Suppose that we want to describe Ba(0.25) Sr(0.75) Ti O3.
The input variables related to the construction of the alchemical Ba(0.25) Sr(0.75)
potential will be :
npsp 4 ! 4 pseudopotentials should be read.
znucl 8 40 56 38 ! The nuclear charges. Note that the two
! atoms whose pseudopotentials are to be mixed
! are mentioned at the end of the series.
ntypat 3 ! There will be three types of atoms.
ntypalch 1 ! One pseudoatom will be alchemical.
! Hence, there will be ntyppure=2 pure pseudoatoms,
! with znucl 8 (O) and 40 (Ti), corresponding to
! the two first pseudopotentials. Out of the
! four pseudopotentials, npspalch=2 are left
! for alchemical purposes, with znucl 56 (Ba)
! and 38 (Sr).
mixalch 0.25 0.75 ! For that unique pseudoatom to be
! generated, here are the mixing coeeficients,
! to be used to combine the Ba and Sr pseudopotentials.
Example 2. More complicated, and illustrate some minor drawback of the
design of input variables.
Suppose that one wants to generate Al(0.25)Ga(0.75) As(0.10)Sb(0.90).
The input variables will be :
npsp 4 ! 4 pseudopotentials should be read
znucl 13 31 33 51 ! The atomic numbers. All pseudopotentials
! will be used for some alchemical purpose
ntypat 2 ! There will be two types of atoms.
ntypalch 2 ! None of the atoms will be "pure".
! Hence, there will be npspalch=4 pseudopotentials
! to be used for alchemical purposes.
mixalch 0.25 0.75 0.0 0.0 ! This array is a (4,2) array, arranged in the
0.0 0.0 0.1 0.9 ! usual Fortran order.
Minor drawback : one should not forget to fill mixalch with the needed zero's, in this later case.
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 Complete list of input variables
natsph
Mnemonics: Number of ATomic SPHeres for the atomprojected densityofstates
Characteristic:
Variable type: integer parameter
Default is natom
This input variable is active only in the
prtdos=3 case.
It gives the number of atoms around which the sphere
for atomprojected densityofstates will be build,
in the prtdos=3 case.
The indices of these atoms is given by iatsph.
The radius of these spheres is given by ratsph.
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 Complete list of input variables
nbdbuf
Mnemonics: Number of BanDs for the BUFfer
Characteristic:
Variable type:
integer parameter
Default 0.
However, the default is changed to 2 in some cases, see later.
nbdbuf gives the number of bands, the highest in energy, that,
among the
nband bands, are to be considered
as part of a buffer. This concept is useful in two situations:
in nonselfconsistent
calculations, for the determination of the convergence tolerance ;
for response functions of metals, to avoid instabilities.
In nonselfconsistent GS calculations (iscf<0),
the highest levels might be
difficult to converge, if they are degenerate with another level,
that does not belong to the set of bands treated. Then, it might
take extremely long to reach tolwfr, although
the other bands are already extremely wellconverged, and the energy
of the highest bands (whose residual are not yet good enough), is
also rather well converged.
In response to this problem, for nonzero nbdbuf, the
largest residual (residm), to be later compared with tolwfr,
will be computed only in the set of nonbuffer bands (this modification
applies for nonselfconsistent as well as selfconsistent calculation,
for GS as well as RF calculations).
For a GS calculation, with iscf<0, supposing
nbdbuf is not initialized in the input file,
then ABINIT will overcome the default nbdbuf value,
and automatically set nbdbuf to 2.
In metallic RF calculations, in the conjugate gradient optimisation
of firstorder wavefunctions, there is an instability situation
when the q wavevector of the perturbation brings the eigenenergy of the
highest treated band at some k point higher than the lowest
untreated eigenenergy at some k+q point.
If one accept a buffer of frozen states, this instability can be made to
disappear. Frozen states receive automatically a residual value of 0.1d0.
For a RF calculation, with 3<=occopt<=7,
supposing
nbdbuf is not initialized in the input file, then
ABINIT will overcome the default nbdbuf value,
and automatically set nbdbuf to 2. This value might be too low
in some cases.
Also, the number of active bands, in all cases, is imposed
to be at least 1, irrespective of the value of nbdbuf.
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 Complete list of input variables
nberry
Mnemonics: Number of BERRY phase computations
Characteristic:
Variable type: integer nberry
Default is 1
Used for nonzero values of berryopt.
Gives the number of Berry phase computations of polarisation,
or finitedifference estimations of the derivative of wavefunctions
with respect to the wavevector,
each of which might be characterized by a different change of
wavevector kberry.
When equal to 0, no Berry phase calculation of polarisation
is performed. The maximal value of nberry is 20.
Note that the computation of the polarisation for a set of bands
having different occupation numbers is meaningless (although
in the case of spinpolarized calculations, the spin up bands
might have an identical occupation number, that might differ
from the identical occupation number of spin down bands).
Although meaningless, ABINIT will perform such computation,
if required by the user. The input variable
bdberry governs the set of bands
for which a Berry phase is computed.
The computation of the Berry phase is not yet implemented
for spinor wavefunctions (nspinor=2).
Moreover, it is not yet implemented in the parallel version of ABINIT.
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 Complete list of input variables
ndivk
Mnemonics: Number of DIVisions of K lines
Characteristic: NOT INTERNAL
Variable type:
integer array ndivk(abs(kptopt))
No default.
Gives the number of divisions of each of the segments
of the band structure, whose path is determined by
kptopt
and
kptbounds.
This is only needed when kptopt
is negative. In this case, the absolute value of
kptopt is the number of such segments.
For example, suppose that the number of segment is just one
(kptopt=1),
a value ndivk=4 will lead to the computation
of points with relative coordinates 0.0, 0.25, 0.5, 0.75 and 1.0 , along
the segment in consideration.
Now, suppose that there are two segments
(kptopt=2), with
ndivk(1)=4 and ndivk(2)=2, the computation of the
eigenvalues will be done at 7 points, 5 belonging to the
first segment, with relative coordinates 0.0, 0.25, 0.5, 0.75 and 1.0,
the last one being also the starting point of the next segment,
for which two other points must be computed, with relative coordinates
0.5 and 1.0 .
It is easy to compute disconnected circuits (nonchained segments),
by separating
the circuits with the value ndivk=1 for the intermediate
segment connecting the end of one circuit with the
beginning of the next one (in which case no intermediate
point is computed along this segment).
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 Complete list of input variables
ngfft
Mnemonics: Number of Grid points for
Fast Fourier Transform
Characteristic:
Variable type: integer array ngfft(3)
Default is 0 0 0 (so, automatic selection
of optimal values)
gives the size of fast fourier transform
(fft) grid in three dimensions. Each number must be
composed of the factors 2, 3, and 5 to be consistent with
the radices available in our fft. If no ngfft is provided or
if ngfft is set to 0 0 0, the code will automatically provide
an optimal set of ngfft values, based on acell,
rprim and ecut.
This is the recommended procedure, of course.
The total number of FFT points
is the product:
ngfft(1)*ngfft(2)*ngfft(3)=nfft .
When ngfft is made smaller
than recommended values, the code runs faster and the
equations in effect are approximated by a low pass fourier
filter. The code reports to standard output (unit 06) a
parameter "boxcut" which is the smallest ratio of the fft
box side to the G vector basis sphere diameter. When
boxcut is less than 2 the fourier filter approximation is being
used. When boxcut gets less than about 1.5 the
approximation may be too severe for realistic results
and should be tested against larger values of ngfft.
When boxcut is larger than 2, ngfft could be reduced without
loss of accuracy. In this case, the small variations
that are observed are solely due to the
xc quadrature, that may be handled with intxc=1
to even reduce this effect.
Internally, ngfft is an array of size 18. The present
components are stored in ngfft(1:3), while
 ngfft(4:6) contains slightly different (larger) values,
modified for efficiency of the FFT
 ngfft(7) is fftalg
 ngfft(8) is fftcache
 ngfft(9) is set to 0 if the parallelization of the FFT is not activated,
while it is set to 1 if it is activated.
 ngfft(10) is the number of processors of the FFT group
 ngfft(11) is the index of the processor in the group of processors
 ngfft(12) is n2proc, the number of xz planes, in reciprocal space, treated by the processor
 ngfft(13) is n3proc, the number of xy planes, in real space, treated by the processor
 ngfft(14) is mpi_comm_fft, the handle on the MPI communicator in charge of the FFT parallelisation
 ngfft(15:18) are not yet used
The number of points stored by this processor in real space is n1*n2*n3proc, while in reciprocal
space, it is n1*n2proc*n3.
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 Complete list of input variables
nline
Mnemonics: Number of LINE minimisations
Characteristic:
Variable type: integer parameter
Default is 4.
Gives maximum number of line minimizations
allowed in preconditioned conjugate gradient minimization
for each band. The Default, 4, is fine.
Special cases, with degeneracies or neardegeneracies
of levels at the Fermi energy may require a larger value of
nline (5 or 6 ?)
Line minimizations will be stopped anyway when improvement
gets small. With the input variable nnsclo,
governs the convergence of the wavefunctions
for fixed potential.
Note that nline=0 can be used to diagonalize the Hamiltonian
matrix in the subspace spanned by the input wavefunctions.
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 Complete list of input variables
npsp
Mnemonics: Number PSeudoPotentials
Characteristic: NO MULTI
Variable type: integer parameter
Default is ntypat
Usually, the number of pseudopotentials to be read is equal
to the number of type of atoms. However,
in the case an alchemical mixing of pseudopotential is to be used,
often the number of pseudopotentials to be read will not equal the number of types of atoms.
Alchemical pseudopotentials will be present
when ntypalch is nonzero.
See ntypalch
to understand how
to use alchemical potentials in ABINIT.
The input variables
ntypalch,
algalch,mixalch)
are active, and generate alchemical potentials from the available
pseudopotentials. Also, the inner variables
ntyppure,npspalch)
becomes active. See these input variables, especially
mixalch, to understand how
to use alchemical potentials in ABINIT.
Go to the top
 Complete list of input variables
npspalch
Mnemonics:
Number of PSeudoPotentials that are "ALCHemical"
Characteristic: Inner
Variable type: integer parameter, nonnegative
npspalch=npspntyppure
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 Complete list of input variables
nqpt
Mnemonics: Number of Q  POINTs
Characteristic:
Variable type: integer parameter
Default is 0.
Determines whether one q point
must be read (See the variables qpt and qptnrm).
Can be either 0 or 1.
If 1 and used in groundstate calculation,
a global shift of all the kpoints is applied, to give
calculation at k+q.
In this case, the output wavefunction will be appended
by _WFQ instead of _WFK (see the section 4 of abinis_help)
Also, if 1 and a RF calculation is done, defines the
wavevector of the perturbation.
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 Complete list of input variables
nspden
Mnemonics: Number of SPinDENsity components
Characteristic: DEVELOP
Variable type: integer parameter
The Default is the value of
nsppol.
If nspden=1, no spinmagnetisation : the density matrix is
diagonal, with same values spinup and spindown
(compatible with nsppol=1 only,
for both nspinor=1 or 2)
If nspden=2, scalar magnetization (the axis is arbitrarily
fixed in the z direction) : the density matrix is
diagonal, with different values for spinup and spindown
(compatible with nspinor=1,
either with nsppol=2 general
collinear magnetisation or
nsppol=1 antiferromagnetism)
If nspden=4, vector magnetization : the density matrix is full,
with allowed x, y and z magnetisation
(useful only with nspinor=2 and
nsppol=1, either
because there is spinorbit without timereversal
symmetry  and thus spontaneous magnetization, or
with spinorbit, if one allows for spontaneous
noncollinear magnetism). Not yet available for forces,
stresses, response functions.
The default (nspden=nsppol)
does not suit the case of vector magnetization.
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 Complete list of input variables
nspinor
Mnemonics:
Number of SPINORial components of the wavefunctions
Characteristic: DEVELOP
Variable type: integer parameter
The Default is 1.
If nspinor=1, usual case : scalar wavefunction
(compatible with (nsppol=1,
nspden=1) as well
as (nsppol=2, nspden=2) )
If nspinor=2, the wavefunction is a spinor
(compatible with nsppol=1, with
nspden=1 or 4,
but not with nsppol=2)
When nspinor is 2, the values of istwfk
are automatically set to 1. Also, the number of bands, for each kpoint,
should be even.
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 Complete list of input variables
ntypalch
Mnemonics:
Number of TYPe of atoms that are "ALCHemical"
Characteristic:
Variable type: integer parameter
The default is 0
Used for the generation of alchemical pseudopotentials :
when ntypalch is nonzero, alchemical mixing
will be used.
Among the ntypat types of atoms, the
last ntypalch will be "alchemical" pseudoatoms, while only
the first ntyppure will be uniquely associated with a pseudopotential
(the ntyppure first of these, actually). The
ntypalch types of alchemical
pseudoatoms are to be made
from the remaining npspalch pseudopotentials.
In this case,
the input variables
algalch,mixalch
are active, and generate alchemical potentials from the available
pseudopotentials. See these input variables, especially
mixalch, to understand how
to use alchemical potentials in ABINIT.
Go to the top
 Complete list of input variables
ntyppure
Mnemonics:
Number of TYPe of atoms that are "PURe"
Characteristic: Inner
Variable type: integer parameter, nonnegative
ntyppure=ntypatntypalch
Go to the top
 Complete list of input variables
occ
Mnemonics: OCCupation numbers
Characteristic: EVOLVING
Variable type: real array occ(nband)
Default : occ is set to 0's.
Gives occupation numbers for all
bands in the problem. Needed if occopt==0 or
occopt==2.
Ignored otherwise. Also ignored when iscf=2.
Typical band occupancy is either
2 or 0, but can be 1 for halfoccupied band or other
choices in special circumstances.
If occopt is not 2,
then the occupancies must be the same for each k point.
If occopt=2, then the band occupancies must be
provided explicitly for each band, EACH k POINT,
and EACH SPINPOLARIZATION, in an
array which runs over all bands, k points,
and spinpolarizations.
The order of entries in the array would correspond to
all bands at the first k point (spin up), then all bands at the
second k point (spin up), etc, then all kpoints spin down.
The total number of array elements
which must be provided is
( nband(1)+nband(2)+...+
nband(nkpt) ) *
nsppol .
The occupation numbers evolve only for metallic occupations,
that is, occopt>=3 .
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 Complete list of input variables
optdriver
Mnemonics: OPTions for the DRIVER
Characteristic:
Variable type: integer parameter
The Default is optdriver=0
For each dataset, choose
the task to be done, at the level of the "driver" routine.
The choice is between :
optdriver=0 : groundstate calculation (GS), routine "gstate"
optdriver=1 : responsefunction calculation (RF), routine "respfn"
optdriver=2 : susceptibility calculation (SUS), routine "suscep"
optdriver=3 : susceptibility and dielectric matrix calculation (CHI), routine "screening"
(see the input variables ecutwfn,
ecuteps,
plasfrq,
getkss,
as well as nbandkss and nband)
optdriver=4 : selfenergy calculation (SIG), routine "sigma"
optdriver=5 : nonlinear response functions, using the 2n+1 theorem, routine "nonlinear"
If one of rfphon, rfelfd,
or rfstrs is nonzero, while optdriver
is not defined in the input file, ABINIT will set optdriver to 1
automatically. These input variables (rfphon,
rfelfd, and rfstrs) must be
zero if optdriver is not set to 1.
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 Complete list of input variables
so_typat
Mnemonics:
SpinOrbit: TYPe of each pseudoATom
pspso (obsolete)
Mnemonics:
PSeudoPotential: treatment of SpinOrbit interaction
Characteristic:
Variable type: integer array
so_typat(ntypat)
Default is ntypat*1
For each type of atom (each pseudopotential), specify
the spinorbit interaction.
If 1 : no spinorbit interaction, even if nspinor=2
If 2 : treat spinorbit in the HGH form
(not allowed for all pseudopotentials)
If 3 : treat spinorbit in the HFN form
(not allowed for all pseudopotentials)
Also, so_typat=0 default to 1, 2, or 3 according
to the data contained in the pseudopotential file
(1= there is no spinorbit information in the psp file;
2= the spinorbit information is of the HGH form;
3= the spinorbit information is of the HFN form )
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 Complete list of input variables
qpt
Mnemonics: Q PoinT
Characteristic:
Variable type: real array of 3 elements
Default wavevector is 0 0 0.
Define a q vector.
See qptnrm for extra normalization.
In groundstate calculation, if nqpt is 1,
the vector
qptn(1:3)=
qpt(1:3)/qptnrm is added to
each renormalized k point
kpt(1:3)/kptnrm
to generate the normalized, shifted, set of kpoints
kptns(1:3,1:nkpt).
In responsefunction calculations,
qptn(1:3)=
qpt(1:3)/qptnrm
is the wavevector of the phonontype calculation.
For insulators, there is no restriction on the
qpoints to be used for the perturbations. By contrast,
for metals, for the time being, it is adviced to take
q points for which the k and k+q grids are the same
(when the periodicity in reciprocal space is taken
into account).
Tests remains to be done to see whether
other q points might be allowed (perhaps with some
modification of the code).
Go to the top
 Complete list of input variables
qptnrm
Mnemonics: Q PoinTs NoRMalization
Characteristic:
Variable type: real parameter
Default is 1.0
Provides renormalization
of qpt.
Must be positive, nonzero.
The actual q vector (renormalized) is
qptn(1:3)=
qpt(1:3)/qptnrm.
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 Complete list of input variables
ratsph
Mnemonics: Radius of the ATomic SPHere
Characteristic:
Variable type: real parameter
Default is 2.0 Bohr
Active only in the
prtdos=3 case, for the time being.
Provides the radius of the spheres around the natsph atoms
of indices iatsph, in which the local
DOS and its angularmomentum projections will be analysed.
Note that, as presently implemented, the SAME radius is used for all the
atoms. So, one might have to perform different calculations to obtain the
set of relevant DOS, each corresponding to one atom type, for each of
which a different radius might be used.
NOTE :
The choice of this radius is quite arbitrary. In a planewave basis set,
there is no natural definition of an atomic sphere. However, it might be wise
to use the following welldefined and physically motivated procedure
(in version 4.2, this procedure is NOT implemented, unfortunately) :
from the Bader analysis, one can define the radius of the sphere
that contains the same charge as the Bader volume. This
"Equivalent Bader charge atomic radius" might then be used to perform
the present analysis.
See the AIM (Bader) help file for more explanations.
Another physically motivated choice would be to rely on another
charge partitioning, like the Hirshfeld one (see the cut3d utility).
The advantage of using charge partitioning schemes comes from the fact that the
sum of atomic DOS, for all angular momenta and atoms, integrated on the
energy range of the occupied states,
gives back the total charge.
If this is not an issue, one could rely on the half of the nearestneighbour distances, or
any scheme that allows to define an atomic radius. Note that the choice of this
radius is however critical for the balance between the s, p and d components. Indeed,
the integrated charge within a given radius, behave as a different power of the
radius, for the different channels s, p, d. At the limit of very small radii, the s component
dominates the charge contained in the sphere ...
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 Complete list of input variables
spinat
Mnemonics: SPIN for AToms
Characteristic:
Variable type:
real array spinat(3,natom)
or spinat(3,natrd) if the symmetriser is used
Default is 0.0d0.
Gives the initial electronic spinmagnetisation
for each atom, in unit of hbar/2.
Note that if nspden=2,
the zcomponent must be given
for each atom, in triplets (0 0 zcomponent).
For example, the electron of an hydrogen atom
can be spin up (0 0 1.0) or spin down (0 0 1.0).
This value is only used to create
the first exchange and correlation potential,
and is not used anymore afterwards.
It is not checked against the initial occupation numbers
occ for each spin channel.
It is meant to give an easy way to break
the spin symmetry, and to allow
to find stable local spin fluctuations, for example :
antiferromagnetism, or the spontaneous spatial
spin separation of elongated H2 molecule.
If the geometry builder is used, spinat will be related
to the preprocessed set of atoms, generated by the
geometry builder. The user must thus foresee the effect
of this geometry builder (see objarf).
If the geometry builder is not used, and the symmetries
are not specified by the user (nsym=0),
spinat will be used, if present, to determine the antiferromagnetic
characteristics of the symmetry operations, see symafm
If the symmetries are specified, and the irreducible set of atoms
is specified, the antiferromagnetic characteristics of the symmetry
operations symafm will be used to generate
spinat for all the nonirreducible atoms.
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 Complete list of input variables
stmbias
Mnemonics: Scanning Tunneling Microscopy BIAS voltage
Characteristic: ENERGY
Variable type: real parameter
Default is 0.00
Gives, in Hartree, the
bias of the STM tip, with respect to the sample, in order to generate
the STM density map.
Used with positive iscf,
occopt=7 (metallic, gaussian),
nstep=1 ,
and positive prtstm, this
value is used to generate a charge density map from electrons
close to the Fermi energy, in a (positive or negative) energy range.
Positive stmbias will lead to the inclusion of occupied (valence) states only, while
negative stmbias will lead to the inclusion of unoccupied (conduction) states only.
Can be specified in Ha (the default), Ry, eV or Kelvin, since
stmbias has the
'ENERGY' characteristics.
0.001 Ha = 27.2113961 meV = 315.773 Kelvin .
With occopt=7,
one has also to specify an independent broadening tsmear.
Go to the top
 Complete list of input variables
symafm
Mnemonics: SYMmetries, AntiFerroMagnetic characteristics
Characteristic:
Variable type:
integer array symafm(nsym)
Default is nsym*1.
In case the material is magnetic (well, this is only interesting in the
case of antiferromagnetism), additional symmetries might appear, that
change the sign of the magnetisation.
They have been introduced by Shubnikov (1951). They can be used by ABINIT
to decrease the CPU time, by using them to decrease the number of kpoints.
symafm should be set to +1 for all the usual symmetry operations,
that do not change the sign of the magnetisation, while it should be
set to 1 for the magnetisationchanging symmetries.
If the symmetry operations are not specified by the user
in the input file, that is, if nsym=0,
then ABINIT will use the values of spinat
to determine the content of symafm.
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 Complete list of input variables
timopt
Mnemonics: TIMing OPTion
Characteristic: NO MULTI, DEVELOP
Variable type:
integer parameter
Default is 1 for sequential code,
2 for parallel code.
This input variable allows to modulate the use of the timing routines.
If 0 => as soon as possible, suppresses all calls to timing routines
If 1 => usual timing behaviour, with short analysis, appropriate
for sequential execution
If 2 => close to timopt=1, except that the analysis routine
does not time the timer, appropriate for parallel execution.
If 1 => a full analysis of timings is delivered
If 2 => a full analysis of timings is delivered,
except timing the timer
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 Complete list of input variables
tphysel
Mnemonics: Temperature (PHYSical) of the ELectrons
Characteristic: ENERGY
Variable type: real parameter
Default is 0.00
Gives, in Hartree, the physical temperature of the
system, in case occopt=4, 5, 6, or 7.
Can be specified in Ha (the default), Ry, eV or Kelvin, since
ecut has the
'ENERGY' characteristics.
0.001 Ha = 27.2113961 meV = 315.773 Kelvin .
One has to specify an independent broadening tsmear.
The combination of the two parameters
tphysel and tsmear is described
in a paper by M. Verstraete and X. Gonze, Phys. Rev. B (2002).
Note that the signification of the entropy is modified with respect
to the usual entropy. The choice has been made to use
tsmear as a prefactor of the entropy,
to define the entropy contribution to the free energy.
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 Complete list of input variables
tsmear
Mnemonics: Temperature of SMEARing
Characteristic: ENERGY
Variable type: real parameter
Default is 0.04
Gives the broadening of occupation
numbers occ, in the metallic cases
(occopt=3, 4, 5, 6 and 7).
Can be specified in Ha (the default), eV, Ry, or Kelvin, since
tsmear has the
'ENERGY' characteristics.
0.001 Ha = 27.2113961 meV = 315.773 Kelvin
Default is 0.04 Ha. This should be OK for a freeelectron
metal like Al. For dband metals, use 0.01 Ha.
Always check the convergence of the calculation
with respect to this parameter, and simultaneously,
with respect to the sampling of kpoints (see nkpt)
If occopt=3, tsmear is the
physical temperature, as the broadening is based on FermiDirac statistics.
However,
if occopt=4, 5, 6, or 7,
the broadening is not based on FermiDirac statistics, and
tsmear is only a convergence parameter. It is still possible
to define a physical temperature, thanks to the input variable
tphysel. See the paper
by M. Verstraete and X. Gonze, Phys. Rev. B (2002).
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 Complete list of input variables
vacuum
Mnemonics: VACUUM identification
Characteristic: NOT INTERNAL
Variable type: integer array vacuum(3)
No Default
Establishes the presence (if 1) or absence (if 0) of a vacuum
layer, along the three possible directions normal to the
primitive axes.
This information might be used to generate kpoint grids,
if kptopt=0 and neither
ngkpt nor kptrlatt
are defined (see explanations with the input variable
prtkpt).
It will allow to select
a zero, one, two or threedimensional
grid of k points. The coordinate of the k points
along vacuum directions is automatically set to zero.
If vacuum is not defined, the input variable
vacwidth
will be used to determine automatically whether the
distance between atoms is sufficient to have the
presence or absence of vacuum.
Go to the top
 Complete list of input variables
vacwidth
Mnemonics: VACuum WIDTH
Characteristic: LENGTH
Variable type: real parameter
Default value is 10.0
Give a minimum "projected" distance between
atoms to be found in order to declare that there
is some vacuum present for each of the three
directions.
By default, given in bohr atomic units
(1 bohr=0.5291772083 Angstroms), although Angstrom can be specified,
if preferred, since vacwidth has the
'LENGTH' characteristics.
The precise requirement is that a slab
of width vacwidth, delimited by two
planes of constant reduced coordinates in the
investigated direction, must be empty of atoms.
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