[Pw_forum] LO -TO Splitting

[Eyvaz Isaev]

Hi,

> 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. 

Did you compare phonon frequencies in dyn-files for USPP and NCPP? If you got wrong (or different) phonon dispersions the phonon DOS will be different, of course.

Did you use a serial or parallel version? Try restart  
your job with NCPP, sometime it helps.

Some additional comments, not related to the issue, but might be useful.

> ecutwfc =18.0, ecutrho =1700
ecutrho for USPP is abnormally large, tipically it is around (8-12) times of ecutwfs. 

> ecutwfc =60.0, ecutrho=450,
ecutrho for NCPP is 4 times of ecutwfc. There is no reason for using larger ecutrho.

Please also specify the Subject correctly, as your topic is not related to LO-TO splitting, definitely.

Bests,
Eyvaz.

-------------------------------------------------------------------
Prof. Eyvaz Isaev, 
Theoretical Physics Department, Moscow State Institute of Steel & Alloys, Russia, 
Department of Physics, Chemistry, and Biology (IFM), Linkoping University, Sweden 
Condensed Matter Theory Group, Uppsala University, Sweden 
Eyvaz.Isaev at fysik.uu.se, isaev at ifm.liu.se, eyvaz_isaev at yahoo.com


--- On Mon, 11/10/08, Shyam <slgphy at rediffmail.com> wrote:

> From: Shyam <slgphy at rediffmail.com>
> Subject: [Pw_forum] LO -TO Splitting
> To: pw_forum at pwscf.org
> Date: Monday, November 10, 2008, 7:10 PM
> 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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