# Finite electric field calculation of AlP at clamped atomic positions
#
# Here the polarization of the cell is computed as a function of increasing
# external homogeneous electric field.
# berryopt 4 is used to trigger the finite field calculation, while
# the efield variable sets the strength (in atomic units) and direction
# of the field
# we can run many (11) fields, or just 3, to make a quick run.
# ndtset 11
ndtset 3
jdtset 11
21 # 22 23 24 25 # The additional 8 values of the field have been suppressed to save CPU time
31 # 32 33 34 35
# the initial run is at zero field and uses berryopt -1
berryopt11 -1 rfdir11 1 1 1
# runs with finite field use berryopt 4, efield, and
# must read in the wavefunctions of the previous run with smaller field
# if variables tagged by numbers like 22, 23, 24, 25 are defined but
# not called by jdtset (above), they will be quietly ignored. This
# feature gives a lot of flexibility in an input file.
berryopt21 4 efield21 0.0001 0.0001 0.0001 getwfk21 11
berryopt22 4 efield22 0.0002 0.0002 0.0002 getwfk22 21
berryopt23 4 efield23 0.0003 0.0003 0.0003 getwfk23 22
berryopt24 4 efield24 0.0004 0.0004 0.0004 getwfk24 23
berryopt25 4 efield25 0.0005 0.0005 0.0005 getwfk25 24
berryopt31 4 efield31 -0.0001 -0.0001 -0.0001 getwfk31 11
berryopt32 4 efield32 -0.0002 -0.0002 -0.0002 getwfk32 31
berryopt33 4 efield33 -0.0003 -0.0003 -0.0003 getwfk33 32
berryopt34 4 efield34 -0.0004 -0.0004 -0.0004 getwfk34 33
berryopt35 4 efield35 -0.0005 -0.0005 -0.0005 getwfk35 34
#Definition of the unit cell
acell 3*7.2728565836E+00
rprim
0.0000000000E+00 7.0710678119E-01 7.0710678119E-01
7.0710678119E-01 0.0000000000E+00 7.0710678119E-01
7.0710678119E-01 7.0710678119E-01 0.0000000000E+00
#Definition of the atom types and pseudopotentials
ntypat 2 # two types of atoms
znucl 15 13 # the atom types are Phosphorous and Aluminum
# the following norm-conserving pseudopotentials are stored in the abinit distribution, but are freely
# available through www.pseudo-dojo.org
# this set uses the Perdew-Wang parameterization of LDA for the xc model
pp_dirpath "$ABI_PSPDIR"
pseudos "Pseudodojo_nc_sr_04_pw_standard_psp8/P.psp8, Pseudodojo_nc_sr_04_pw_standard_psp8/Al.psp8"
#Definition of the atoms
natom 2 # two atoms in the cell
typat 1 2 # type 1 is Phosphorous, type 2 is Aluminum (order defined by znucl above and pseudos list)
nband 4 # nband is restricted here to the number of filled bands only, no empty bands. The theory of
# the Berrys phase polarization formula assumes filled bands only. Our pseudopotential choice
# includes 5 valence electrons on P, 3 on Al, for 8 total in the primitive unit cell, hence
# 4 filled bands.
#atomic positions, given in units of the cell vectors. Thus as the cell vectors
#change due to strain the atoms will move as well.
xred
1/4 1/4 1/4
0 0 0
#Numerical parameters of the calculation : planewave basis set and k point grid
ecut 5 # this value is very low but is used here to achieve very low calculation times.
# in a production environment this should be checked carefully for convergence and
# a more reasonable value is probably around 20
ecutsm 0.5
dilatmx 1.05
ngkpt 6 6 6
nshiftk 4 # this Monkhorst-Pack shift pattern is used so that the symmetry of the shifted grid
# is correct. A gamma-centered grid would also have the correct symmetry but would be
# less efficient.
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
#Parameters for the SCF procedure
nstep 8
toldfe 1.0d-15
# suppress printing of density and eigenvalues for this tutorial,
# but we do need the wavefunctions
prtwf 1
prtden 0
prteig 0
##############################################################
# This section is used only for regression testing of ABINIT #
##############################################################
#%%
#%% [setup]
#%% executable = abinit
#%% [files]
#%% files_to_test =
#%% tffield_6.abo, tolnlines= 0, tolabs= 1.001e-04, tolrel= 5.000e-04, fld_options = -ridiculous
#%% [paral_info]
#%% max_nprocs = 2
#%% [extra_info]
#%% authors = J. Zwanziger, M. Veithen
#%% keywords = NC, DFPT
#%% description = Finite electric field calculation of AlP at clamped atomic positions
#%%