This document describes several important internal variables, to which the user has no direct access through a keyword, but that are derived from the input variables at the time of their processing and used internally. Their value is fixed for a specific dataset. They are present in the dtset array, in addition to the input variables that can be directly addressed by the user.

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

When the user is sufficiently familiarized with ABINIT, the file ~abinit/doc/users/tuning.txt will be useful; this file provides tips on optimizing the performance of ABINIT. For response-function calculations using ABINIT, please read the response function help file

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 list of contributors, see ~abinit/doc/developers/contributors.txt.

A.

B.

C.

D.

E.

F.

G.

H.

I.

J.

K. kptns

L.

M. mband mgfft mgfftdg mpw

N. natpawu ndynimage nfft nfftdg nelect

O.

P.

Q. qptn

R.

S.

T.

U. usepaw userec

V.

W.

X.

Y.

Z. ziontypat

kptns

Mnemonics: K-PoinTs re-Normalized and Shifted

Characteristic: INTERNAL

Variable type: real array

If nqpt=0, or if one is
doing a reponse calculation,
this internal variable is derived from
kpt and kptnrm:
**kptns**(1:3,:)=
kpt(1:3,:)/
kptnrm, so that
it is kpt renormalized by
kptnrm.

If nqpt=1 and one is
not doing a ground-state calculation,
this internal variable is derived from
kpt,kptnrm
and qptn
**kptns**(1:3,:)=
kpt(1:3,:)/
kptnrm+
qptn(1:3), so that
it is kpt renormalized by
kptnrm, then shifted
by qptn(1:3).

Go to the top
** | **Complete list of input variables

mband

Mnemonics: Maximum number of BANDs

Characteristic: INTERNAL

Variable type: integer

This internal variable derives
the maximum number of bands
over all k-points and spin-polarisation from
nband(1:nkpt*nsppol).

Go to the top
** | **Complete list of input variables

mgfft

Mnemonics: Maximum of nGFFT

Characteristic: INTERNAL

Variable type: integer

This internal variable contains the maximum of
ngfft(1:3).

Go to the top
** | **Complete list of input variables

mgfftdg

Mnemonics: Maximum of nGFFT for the Double Grid

Characteristic: INTERNAL

Variable type: integer

This internal variable contains the maximum of
ngfftdg(1:3).

Go to the top
** | **Complete list of input variables

mpw

Mnemonics: Maximum number of Plane Waves

Characteristic: INTERNAL

Variable type: integer

This internal variable gives the maximum of the number of
plane waves over all k-points. It is computed
from ecut and the description
of the cell, provided by
acell,
rprim, and/or
angdeg.

Go to the top
** | **Complete list of input variables

natpawu

Mnemonics: Number of AToms on which PAW+U is applied

Characteristic: INTERNAL

Variable type: integer parameter

This internal variable gives the number of atoms on which LDA/GGA+U method
is applied.

It is determined by natom,
usepawu and
lpawu input keywords.

Go to the top
** | **Complete list of input variables

ndynimage

Mnemonics: Number of DYNamical IMAGEs

Characteristic: INTERNAL

Variable type: integer

This internal variable gives the number of dynamical images,
immediately deduced from the number of non-zero values present in
dynimage.
It is used to dimension many memory-consuming arrays (one copy for each image),
in case they are not stored on disk (see mkmem),
e.g. the wavefunction array (cg), the density array (rho), etc .

Go to the top
** | **Complete list of input variables

nelect

Mnemonics: Number of ELECTrons

Characteristic: INTERNAL

Variable type: real number

This internal variable gives the number of electrons per unit
cell, as computed from the sum of the valence electrons
related to each atom (given in the pseudopotential, where it is called
"zion"), and the input variable
charge:

**nelect**=zion-charge.

Go to the top
** | **Complete list of input variables

nfft

Mnemonics: Number of FFT points

Characteristic: INTERNAL

Variable type: integer

If space parallelisation is not used,
this internal variable gives the number of Fast Fourier Transform
points in the grid generated by
ngfft(1:3). It is simply the
product of the three components of ngfft.

If space parallelisation is used, then it becomes the
number of Fast Fourier Transform points attributed to the
particular processor. It is no longer the above-mentioned simple product,
but a number usually close to this product divided by the
number of processors on which the space is shared.

Go to the top
** | **Complete list of input variables

nfftdg

Mnemonics: Number of FFT points for the Double Grid

Characteristic: INTERNAL

Variable type: integer

If space parallelisation is not used,
this internal variable gives the number of Fast Fourier Transform
points in the (double) grid generated by
ngfftdg(1:3). It is simply the
product of the three components of ngfftdg.

If space parallelisation is used, then it becomes the
number of Fast Fourier Transform points attributed to the
particular processor. It is no longer the above-mentioned simple product,
but a number usually close to this product divided by the
number of processors on which the space is shared.

Go to the top
** | **Complete list of input variables

qptn

Mnemonics: Q-PoinT re-Normalized

Characteristic: INTERNAL

Variable type: real array

Only used if nqpt=1.

In ground-state calculation,
the vector **qptn**(1:3) is added to
each renormalized k point (whatever the value of
kptopt that was used)
to generate the normalized, shifted, set of k-points
kptns(1:3,1:**nkpt**).

In response-function calculations,
**qptn**(1:3)
is the wavevector of the phonon-type calculation.
**qptn**(1:3) can be produced on the basis of
the different methods described in qptopt,
like using qpt(1:3)
with renormalisation provided by qptnrm,
or using the other possibilities defined by
iqpt,
ngqpt,
nshiftq,
qptrlatt,
shiftq,

For insulators, there is no restriction on the
q-points to be used for the perturbations. By contrast,
for metals, for the time being, it is advised 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 remain 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

usepaw

Mnemonics: USE Projector Augmented Waves method

Characteristic: INTERNAL

Variable type: integer parameter

Default is set by the pseudopotential files : either PAW (1) or norm-conserving (0).

This variable is determined by the pseudopotentials files.
PAW calculations (see PAW variables) can only
be performed with PAW atomic data input files, while
pseudopotential calculations are performed in ABINIT with norm-conserving
pseudopotential input files. Most functionalities in ABINIT are available
with either type of calculation.

Go to the top
** | **Complete list of input variables

userec

Mnemonics: USE RECursion

Characteristic: INTERNAL

Variable type: integer parameter

Default is Value is 0

This internal variable is set to 1 when the recursion method is
activated (see tfkinfunc).

Go to the top
** | **Complete list of input variables

ziontypat

Mnemonics: Z (charge) of the IONs for the different TYPes of AToms

Characteristic:

Variable type: real array ziontypat(ntypat)

Default is value is set by the pseudopotential files.

Charge of the pseudo-ion (=number of valence electrons
that are needed to screen exactly the pseudopotential).

Go to the top
** | **Complete list of input variables