[Pw_forum] Wrong effective charges in AFM insulator using "zue"
xirainbow
nkxirainbow at gmail.com
Wed Jan 19 09:27:29 CET 2011
In 4.2.1 manual, it is said that:*If .zue=true.is an alternative
algorithm, different from the default one (if trans .and. epsil ) The
results should be the same within numerical noise.*
*However, I get wrong "effective charges" in zue=true in AFM insulator
CaMnO3 with **4.2.1*
***These two Mn atoms are the same except antiparallel spin.*
*In "epsil+trans", effective charges of Mn1=7.79, Mn2=7.78;*
*In "zue" , effective charges of Mn1=3.1, Mn2=51.2;*
I will describe my calculation procedure using *4.2.1* in short.
1: I do scf calculation in scf.in
*restart_mode = 'from_scratch'*
*occupations = 'smearing'*
*smearing = 'gauss'*
*degauss = 0.002*
*starting_magnetization(1) = 1*
*starting_magnetization(2) = -1*
*starting_magnetization(3) = 0*
*starting_magnetization(4) = 0*
2: I do a scf calculation in scf.in
*restart_mode = 'restart'*
*occupations = 'fixed'*
*nspin = 2*
*tot_magnetization = 0*
3: I do ph calculation with
*
zue = .TRUE. !the same with epsil and trans = TRUE
(In this condition, effective charges of Mn1=3.1, Mn2=51.2;)
or with:
epsil = .TRUE. , trans = .TRUE.
*
(In this condition *, *effective charges of Mn1=7.79, Mn2=7.78;)
(The reason is why I restart scf is below:
"starting_magnetization" must be used with "smearing". However, "smearing"
will give a metal result. Effective charges can not be calculated for metal.
But, CaMnO3 is really a insulator AFM.
"occupations=fixed" can get a insulator result. However it must used with
"tot_magnetization". If I use "tot_magnetization=0", I will get a PM no AFM
state.
In the end, I use "smearing"+"starting_magnetization" to get a AFM metal.
Then I use "fixed"+"tot_magnetization" to get a AFM insulator.
*Is there any other good method to get a AFM insulator?*)
The following my script for "*zue= .TRUE *"
And I have attached output file of "*zue= .TRUE *" in accessary. Thanks:)
#*********************************************
# scf-antimag-smearing
cat>scf.in<<EOF
for vc-relax
&CONTROL
calculation = 'scf'
title = 'G-10-scf'
verbosity = 'high'
restart_mode = 'from_scratch'
wf_collect = .FALSE.
tstress = .TRUE.
tprnfor = .TRUE.
prefix = 'G-10-scf'
etot_conv_thr = 1.0e-4
forc_conv_thr = 1.0e-3
disk_io = 'low'
pseudo_dir = './'
/
&SYSTEM
ibrav = 2
celldm = 14.20419765
nat = 10
ntyp = 4
nbnd = 50
ecutwfc = 70
ecutrho = 560
nosym = .FALSE.
!nosym_evc = .TRUE.
!noinv = .TRUE.
occupations = 'smearing'
smearing = 'gauss'
degauss = 0.002
starting_magnetization(1) = 1
starting_magnetization(2) = -1
starting_magnetization(3) = 0
starting_magnetization(4) = 0
!occupations = 'fixed'
nspin = 2
!tot_magnetization = 0
/
&ELECTRONS
electron_maxstep = 100
conv_thr = 1.0e-7
mixing_mode = 'plain'
mixing_beta = 0.7
mixing_ndim = 8
diagonalization = 'david'
diago_david_ndim = 4
/
ATOMIC_SPECIES
Mn1 55 Mn.pbe-sp-van.UPF
Mn2 55 Mn.pbe-sp-van.UPF
Ca 40 Ca.pbe-nsp-van.UPF
O 16 O.pbe-rrkjus.UPF
ATOMIC_POSITIONS {crystal}
Mn1 0.00 0.00 0.00
Mn2 0.50 0.50 0.50
Ca 0.25 0.25 0.25
Ca 0.75 0.75 0.75
O 0.75 0.25 0.75
O 0.25 0.75 0.25
O 0.75 0.75 0.25
O 0.25 0.25 0.75
O 0.25 0.75 0.75
O 0.75 0.25 0.25
K_POINTS {automatic}
6 6 6 0 0 0
EOF
./dopw <scf.in >G-scf-10-smearing.out
# scf-antimag-insulator
cat>scf.in<<EOF
for vc-relax
&CONTROL
calculation = 'scf'
title = 'G-10-scf'
verbosity = 'high'
restart_mode = 'restart'
wf_collect = .FALSE.
tstress = .TRUE.
tprnfor = .TRUE.
prefix = 'G-10-scf'
etot_conv_thr = 1.0e-4
forc_conv_thr = 1.0e-3
disk_io = 'low'
pseudo_dir = './'
/
&SYSTEM
ibrav = 2
celldm = ${lattic_parameter} !bohr
nat = 10
ntyp = 4
nbnd = 50
ecutwfc = 70
ecutrho = 560
nosym = .FALSE.
!nosym_evc = .TRUE.
!noinv = .TRUE.
!occupations = 'smearing'
!smearing = 'gauss'
!degauss = 0.002
!starting_magnetization(1) = 1
!starting_magnetization(2) = -1
!starting_magnetization(3) = 0
!starting_magnetization(4) = 0
occupations = 'fixed'
nspin = 2
tot_magnetization = 0
/
&ELECTRONS
electron_maxstep = 100
conv_thr = 1.0e-7
mixing_mode = 'plain'
mixing_beta = 0.7
mixing_ndim = 8
diagonalization = 'david'
diago_david_ndim = 4
/
ATOMIC_SPECIES
Mn1 55 Mn.pbe-sp-van.UPF
Mn2 55 Mn.pbe-sp-van.UPF
Ca 40 Ca.pbe-nsp-van.UPF
O 16 O.pbe-rrkjus.UPF
ATOMIC_POSITIONS {crystal}
Mn1 0.00 0.00 0.00
Mn2 0.50 0.50 0.50
Ca 0.25 0.25 0.25
Ca 0.75 0.75 0.75
O 0.75 0.25 0.75
O 0.25 0.75 0.25
O 0.75 0.75 0.25
O 0.25 0.25 0.75
O 0.25 0.75 0.75
O 0.75 0.25 0.25
K_POINTS {automatic}
6 6 6 0 0 0
EOF
./dopw <scf.in >G-scf-10-insulator.out
#for phonon-antimag
cat>ph.in <<EOF
for phonon
&INPUTPH
amass(1) = 55
amass(2) = 55
amass(3) = 40
amass(4) = 16
outdir = "./"
prefix = 'G-10-scf' !must be the same with scf
ldisp = .FALSE.
niter_ph = 100
tr2_ph = 1.0e-12
alpha_mix(1)= 0.7
nmix_ph = 4
iverbosity = 1
fildyn = 'matdyn'
!epsil = .TRUE. !Do not set epsil to .true. for metallic system or
q/=0
!trans = .TRUE. !if trans .and. epsil effective charges are calculated
zue = .TRUE. !the same with epsil and trans = TRUE
/
0.0 0.0 0.0
EOF
./doph <ph.in >G-ph-10.out
done
#*********************************************
--
____________________________________
Hui Wang
School of physics, Fudan University, Shanghai, China
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