[Pw_forum] PbSe Pseudopotential from PSlibrary

[Rui Mao]

Hi QE users,

I am trying to do some calculations for bulk PbSe, which is simple rocksalt
structure with 2 atoms in the unit cell.
The pseudo I am using are as follows:
Pb.pz-dn-rrkjus_psl.0.2.2.UPF
Se.pz-n-rrkjus_psl.0.2.UPF

However, these PP can not generate the correct phonon dispersion and the
TO-LO splitting at Gamma point is also
considerably underestimated. Experimental data is around 85cm-1, while I am
getting 12cm-1.

I understand that this may due to the effect Spin-Orbital Coupling is not
included in the calculation, since I am using non-relativistic PPs.

Recently published papers have mentioned that they are using
"Pb.rel-pz-nc.UPF" and "Se.rel-pz-nc.UPF" files
from PSlibrary for bulk PbSe phonon calculations.

However, I checked the PSlibrary0.2.5 patch and could not find
"Pb.rel-pz-nc.UPF" and "Se.rel-pz-nc.UPF" files.

I am wondering whether any of you happen to have those PP files, if so
could you please send them to me?

Any suggestion on how to improve the phonon dispersion is also appreciated!

Thank you,
Rui Mao

My input files:

*SCF.in:*

&control
    calculation = 'scf',
    restart_mode='from_scratch',
    wf_collect = .true.,
    prefix='PbSe',
    tstress = .true.
    tprnfor = .true.
    forc_conv_thr = 1.0D-3,
    etot_conv_thr = 1.0D-4,
    pseudo_dir = 'xxx',
    outdir='xxx',
 /
 &system
    ibrav=2, celldm(1) =11.4236, nat=2, ntyp= 2,
    ! lspinorb=.true.,
    ! noncolin=.true.,
    ecutwfc =50,
    ecutrho=700,
    ! occupations='smearing', smearing='mp', degauss=0.01,
 /
 &electrons
    diagonalization='david',
    mixing_mode = 'plain',
    mixing_beta = 0.5,
    conv_thr =  1.0d-8,
/
ATOMIC_SPECIES
Pb   207.2  Pb.pz-dn-rrkjus_psl.0.2.2.UPF
Se   78.96  Se.pz-n-rrkjus_psl.0.2.UPF
ATOMIC_POSITIONS {crystal}
Pb       0.000000000   0.000000000    0.000000000
Se       0.500000000   0.500000000    0.500000000
K_POINTS {automatic}
10 10 10 0 0 0

*PH.in:*

phonons of PbSe_bulk
 &inputph
  tr2_ph=1.0d-16,
  alpha_mix(1)=0.5,
  prefix='PbSe',
  ldisp=.true.,
  epsil=.true.,
  recover=.false.,
  reduce_io=.true.,
  amass(1)=207.2,
  amass(2)=78.96,
  nq1=6, nq2=6, nq3=6,
    outdir='XXX',
  fildyn='PbSe.dyn'
 /

-- 
Rui Mao
============================================================
Department of Electrical and Computer Engineering (ECE)
North Carolina State University (NCSU)
Raleigh, NC, 27606
Email: ruimao20 at gmail.com
============================================================
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