[QE-users] Spin-orbit coupling (SOC) calculation with ultrasoft pseudopotential (USPP) using QE?

[Pacome NGUIMEYA]

Dear QE users,

I recently calculated the band structure of the Tantalum Arsenide (TaAs)
with SOC using the Projector Augmented Wave (PAW) pseudopotential. I got a
result which is not consistent with what exists in the literature.
Actually, when we include the SOC a small gap should open up at the Fermi
level.

To perform that calculation, I added the following three line in my SCF
input files

    *lspinorb = .true.,*
*    noncolin = .true.,*
*    starting_magnetization = 0.0,*

as did in Quantum Espresso Example 7:
https://github.com/maxhutch/quantum-espresso/blob/master/PW/examples/example07/run_example
and
explained here:
https://www.quantum-espresso.org/Doc/pw_user_guide/node10.html

I thought of changing the pseudopotential (PAW) that I used in order to see
if I get a better result.
So, I thought of using the ultrasoft pseudopotential (USPP) but I found
this link
https://www.researchgate.net/post/If_I_would_like_to_add_spin-orbit_coupling_in_band_structure_calculations_what_changes_should_I_do_in_the_input_file_in_Quantum_ESPRESSO
where
it is said that the option *lspinorb= .TRUE.* works only for PAW potentials
and is not supported for ultrasoft pseudopotentials.

*Are the ultrasoft pseudopotentials not supported for SOC calculation in
QE?*

Below is the input file that I used to perform the SOC calculation

&CONTROL
calculation = 'scf',
      prefix = 'TaAs',
                restart_mode = 'from_scratch',
                  pseudo_dir = './',
                      outdir = './',
       etot_conv_thr = 1.0e-5,
  wf_collect = .true.

/
&SYSTEM
                       ibrav = 7,
                           A = 3.4348002616,
   B = 3.4348002616,
   C = 11.641,
       cosAB = 0,
       cosAC = 0,
       cosBC = 0,
                         nat = 8,
                        ntyp = 2,
                     ecutwfc = 65,
                     ecutrho = 400,
          occupations = 'smearing',
                    smearing = 'M-P',
                     degauss = 0.010,
    noncolin = .true.,
    lspinorb = .true.,
   starting_magnetization(1) = 0.0

/
&ELECTRONS
            conv_thr = 1.0e-11,
         mixing_mode = 'plain',
                 mixing_beta = 0.7,
             diagonalization = 'cg'
/
 ATOMIC_SPECIES
   Ta   180.94788  Ta.rel-pbe-spn-kjpaw_psl.0.2.UPF
   As   74.9216    As.rel-pbe-n-kjpaw_psl.0.2.UPF
 ATOMIC_POSITIONS {crystal}
Ta      -0.124991858   0.064689851   0.147167066
Ta       0.875311297   0.310797136   0.394149993
Ta      -0.623651114   0.938399569   0.521894272
Ta       0.374704885   0.186136223   0.769306698
As       0.374135075  -0.312099362   0.271944874
As       0.374998589   0.438122101   1.021399771
As      -0.125251295   0.561961687   0.646512176
As       0.874744421  -0.188007205  -0.104374866
 K_POINTS {automatic}
  09 09 09  1 1 1


Thanks
Pacome
*___*
*_____________*Pacome NGUIMEYA
Ph.D. Candidate
Computational Condensed Matter Physics
University of Cape Town (UCT), South Africa
*“Be Yourself; everyone else is already taken.” *
*Oscar Wilde*
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