[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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