[Pw_forum] LO -TO Splitting

Mon Nov 10 17:10:24 CET 2008

Hello all,I am trying to get the LO-TO splitting in GaAs. But I am
a bit confused about the pseudo potential to be used.  I have done
calculations using both the ultrasoft pseudopotential (USPP)  and
the normconserving (NCPP). Both of these are giving me almost similar
electronic DOS whereas  phonon DOS differ in two cases. The phonon DOS which I have got using USPP is matching with
the reported one and that I have got using NCPP is not matching. The input files used in two cases are as follows,***********************************************************************USPP*********************************************************************** 

cat > gaas.scf.in << EOF 

&control

calculation='scf'

restart_mode='from_scratch',

tstress = .true.

tprnfor = .true.

prefix='gaas',

pseudo_dir = '$PSEUDO_DIR/',

outdir='$TMP_DIR/'

/

&system

ibrav= 2, celldm(1) =10.68, nat= 2, ntyp= 2,

ecutwfc =18.0, ecutrho =1700,

/

&electrons

conv_thr = 1.0d-8

mixing_beta = 0.7

/

ATOMIC_SPECIES

Ga 69.72 Ga.pbe-nsp-van.UPF

As 74.92 As.pbe-n-van.UPF

ATOMIC_POSITIONS

Ga 0.00 0.00 0.00

As 0.25 0.25 0.25

K_POINTS {automatic}

4 4 4 0 0 0 

EOF

$ECHO " running the scf calculation...c"

$PW_COMMAND < gaas.scf.in > gaas.scf.out

check_failure $?

$ECHO " done"

# DOS calculation for GaAs

cat > gaas.dos.in << EOF

&control

calculation='nscf'

prefix='gaas',

pseudo_dir = '$PSEUDO_DIR/',

outdir='$TMP_DIR/'

/

&system

ibrav=2, celldm(1) =10.68, nat=2, ntyp=2,

ecutwfc = 18.0, ecutrho = 1700.0, nbnd=10,

occupations='tetrahedra'

/

&electrons

conv_thr = 1.0e-10

mixing_beta = 0.7 

/

ATOMIC_SPECIES

Ga 69.720 Ga.pbe-nsp-van.UPF

As 74.922 As.pbe-n-van.UPF

ATOMIC_POSITIONS

Ga 0.0 0.0 0.0

As 0.25 0.25 0.25

K_POINTS {automatic}

12 12 12 0 0 0

EOF

cat > gaas.dos2.in << EOF

&inputpp

outdir='$TMP_DIR/'

prefix='gaas'

fildos='gaas.dos',

Emin=-25.0, Emax=25.0, DeltaE=0.1

/

EOF

$ECHO " running DOS calculation for GaAs...c"

$PW_COMMAND < gaas.dos.in > gaas.dos.out

check_failure $?

$DOS_COMMAND < gaas.dos2.in > gaas.dos2.out

check_failure $?

$ECHO " done"

# phonon calculation on a (444) uniform grid of q-points

cat > gaas.ph.in << EOF

phonons of GaAs

&inputph

tr2_ph=1.0d-12,

prefix='gaas',

ldisp=.true.,

nq1=4, nq2=4, nq3=4

amass(1)=69.72,

amass(2)=74.92,

outdir='$TMP_DIR/',

fildyn='gaas.dyn',

/

EOF

$ECHO " running the phonon calculation ...c"

$PH_COMMAND < gaas.ph.in > gaas.ph.out

check_failure $?

$ECHO " done"

cat > q2r.in <<EOF

&input

fildyn='gaas.dyn', zasr='simple', flfrc='gaas444.fc'

/

EOF

$ECHO " transforming C(q) => C(R)...c"

$Q2R_COMMAND < q2r.in > q2r.out

check_failure $?

$ECHO " done"

cat > matdyn.in <<EOF

&input

asr='simple', amass(1)=69.72, amass(2)=74.922,

flfrc='gaas444.fc', flfrq='gaas.freq'

/

9

0.000 0.0 0.0 0.0

0.125 0.0 0.0 0.0

0.250 0.0 0.0 0.0

0.375 0.0 0.0 0.0

0.500 0.0 0.0 0.0

0.625 0.0 0.0 0.0

0.750 0.0 0.0 0.0

0.875 0.0 0.0 0.0

1.000 0.0 0.0 0.0

EOF

$ECHO " recalculating omega(q) from C(R)...c"

$MATDYN_COMMAND < matdyn.in > matdyn.out

check_failure $?

$ECHO " done"

cat > phdos.in <<EOF

&input

asr='simple', dos=.true. amass(1)=69.72, amass(2)=74.922,

flfrc='gaas444.fc', fldos='gaas.phdos', nk1=6,nk2=6,nk3=6

/

EOF

$ECHO " calculating phonon DOS ...c"

$MATDYN_COMMAND < phdos.in > phdos.out

check_failure $?

$ECHO " done"

$ECHO$ECHO "$EXAMPLE_DIR: done"***********************************************************NCPP***********************************************************

cat > gaas.scf.in << EOF

&control

calculation='scf'

restart_mode='from_scratch',

tstress = .true.

tprnfor = .true.

prefix='gaas',

pseudo_dir = '$PSEUDO_DIR/',

outdir='$TMP_DIR/'

/

&system

ibrav= 2, celldm(1) =10.68, nat= 2, ntyp= 2,

ecutwfc =60.0, ecutrho=450,

/

&electrons

conv_thr = 1.0d-8

mixing_beta = 0.7

/

ATOMIC_SPECIES

Ga 69.72 Ga.pz-bhs.UPF

As 74.92 As.gon.UPF

ATOMIC_POSITIONS

Ga 0.00 0.00 0.00

As 0.25 0.25 0.25

K_POINTS {automatic}

4 4 4 0 0 0

EOF

$ECHO " running the scf calculation...c"

$PW_COMMAND < gaas.scf.in > gaas.scf.out

check_failure $?

$ECHO " done"

# DOS calculation for GaAs

cat > gaas.dos.in << EOF

&control

calculation='nscf'

prefix='gaas',

pseudo_dir = '$PSEUDO_DIR/',

outdir='$TMP_DIR/'

/

&system

ibrav=2, celldm(1) =10.68, nat=2, ntyp=2,

ecutwfc = 60.0, ecutrho = 450.0, nbnd=10,

occupations='tetrahedra'

/

&electrons

conv_thr = 1.0e-10

mixing_beta = 0.7 

/

ATOMIC_SPECIES

Ga 69.720 Ga.pz-bhs.UPF

As 74.922 As.gon.UPF

ATOMIC_POSITIONS

Ga 0.0 0.0 0.0

As 0.25 0.25 0.25

K_POINTS {automatic}

12 12 12 0 0 0

EOF

cat > gaas.dos2.in << EOF

&inputpp

outdir='$TMP_DIR/'

prefix='gaas'

fildos='gaas.dos',

Emin=-25.0, Emax=25.0, DeltaE=0.1

/

EOF

$ECHO " running DOS calculation for GaAs...c"

$PW_COMMAND < gaas.dos.in > gaas.dos.out

check_failure $?

$DOS_COMMAND < gaas.dos2.in > gaas.dos2.out

check_failure $?

$ECHO " done"
# phonon calculation on a (444) uniform grid of q-points 
cat > gaas.ph.in << EOF 
phonons of GaAs 
&inputph 
tr2_ph=1.0d-12, 
prefix='gaas', 
ldisp=.true., 
nq1=4, nq2=4, nq3=4 
amass(1)=69.72, 
amass(2)=74.92, 
outdir='$TMP_DIR/', 
fildyn='gaas.dyn', 
/ 
EOF 
$ECHO " running the phonon calculation ...c" 
$PH_COMMAND < gaas.ph.in > gaas.ph.out 
check_failure $? 
$ECHO " done" 
cat > q2r.in <<EOF 
&input 
fildyn='gaas.dyn', zasr='simple', flfrc='gaas444.fc' 
/ 
EOF 
$ECHO " transforming C(q) => C(R)...c" 
$Q2R_COMMAND < q2r.in > q2r.out 
check_failure $? 
$ECHO " done" 
cat > matdyn.in <<EOF 
&input 
asr='simple', amass(1)=69.72, amass(2)=74.922, 
flfrc='gaas444.fc', flfrq='gaas.freq' 
/ 
9 
0.000 0.0 0.0 0.0 
0.125 0.0 0.0 0.0 
0.250 0.0 0.0 0.0 
0.375 0.0 0.0 0.0 
0.500 0.0 0.0 0.0 
0.625 0.0 0.0 0.0 
0.750 0.0 0.0 0.0 
0.875 0.0 0.0 0.0 
1.000 0.0 0.0 0.0 
EOF 
$ECHO " recalculating omega(q) from C(R)...c" 
$MATDYN_COMMAND < matdyn.in > matdyn.out 
check_failure $? 
$ECHO " done" 
cat > phdos.in <<EOF 
&input 
asr='simple', dos=.true. amass(1)=69.72, amass(2)=74.922, 
flfrc='gaas444.fc', fldos='gaas.phdos', nk1=6,nk2=6,nk3=6 
/ 
EOF 
$ECHO " calculating phonon DOS ...c" 
$MATDYN_COMMAND < phdos.in > phdos.out 
check_failure $? 
$ECHO " done" 
$ECHO 
$ECHO "$EXAMPLE_DIR: done"***********************************************************I will be highly thankful if one could please let me know the way out to this.Thank you.Shyam Lal GuptaIIT KanpurKanpurINDIA-208016.
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