====== Spin-orbit coupling bandstructure calculation without magnetic moment ======

Spin-orbit coupling bandstructure calculation without magnetic moment for GaAs

There are two steps, the first step is SCF calculation, and the second is NONSCF calculation.

===== First Step: SCF calculation =====

==== Input files ====

atom.config

<code bash>
     4
 LATTICE
      4.38647521     0.00000000     0.00000000
     -2.19323810     3.79879878     0.00000000
      0.00000000     0.00000000     7.15850229
 POSITION
  34     0.66666667     0.33333333     0.87584179 1 1 1
  34     0.33333333     0.66666667     0.37584179 1 1 1
  48     0.66666667     0.33333333     0.50004945 1 1 1
  48     0.33333333     0.66666667     0.00004945 1 1 1
</code>

etot.input

<code bash>
 1  4
 JOB = SCF
 IN.PSP1 = Cd.SG15.PBE.SOC.UPF
 IN.PSP2 = Se.SG15.PBE.SOC.UPF
 IN.ATOM = atom.config
 CONVERGENCE = difficult
 SPIN = 22
 Ecut = 50
 Ecut2 = 100
 MP_N123 = 12 12 5 0 0 0
 XCFUNCTIONAL = PBE
</code>

  - Spin: specifies spin polarization, 22:Spin-orbit coupling, but without magnetic moment.
  - CONVERGENCE: control the convergence parameters of the SCF self-consistent iteration, possible values: easy or difficult.


Cd.SG15.PBE.SOC.UPF, Se.SG15.PBE.SOC.UPF

<WRAP warning>
Spin-orbit pseudopotential files need to be used.
</WRAP>

==== Calculations ====

  - You can submit PWmat tasks in different ways:

<code bash>
   mpirun -np 4 PWmat | tee output
</code>

<wrap round tip> Run the command directly </wrap>

<code bash>
   #!/bin/bash
   #PBS -N SCF
   #PBS -l nodes=1:ppn=4
   #PBS -q batch
   #PBS -l walltime=100:00:00

   ulimit -s unlimited
   cd $PBS_O_WORKDIR

   mpirun -np 4 PWmat | tee output
</code>

<wrap round tip> Submit the task with a pbs script </wrap>

===== Second Step: NONSCF calculation =====

==== Input files ====

atom.config

<code bash>
     4
 LATTICE
      4.38647521     0.00000000     0.00000000
     -2.19323810     3.79879878     0.00000000
      0.00000000     0.00000000     7.15850229
 POSITION
  34     0.66666667     0.33333333     0.87584179 1 1 1
  34     0.33333333     0.66666667     0.37584179 1 1 1
  48     0.66666667     0.33333333     0.50004945 1 1 1
  48     0.33333333     0.66666667     0.00004945 1 1 1
</code>

etot.input

<code bash>
 1  4
 JOB = NONSCF
 IN.PSP1 = Cd.SG15.PBE.SOC.UPF
 IN.PSP2 = Se.SG15.PBE.SOC.UPF
 IN.ATOM = atom.config
 SPIN = 22
 Ecut = 50
 Ecut2 = 100
 XCFUNCTIONAL = PBE
 IN.VR = T
 IN.KPT = T
</code>

<WRAP round help>
  - Read IN.VR from previous SCF calculation. To copy OUT.VR and OUT.FERMI from the SCF calculation to your current working drectory and rename IN.VR.
  - IN.KPT is the k-points file which PWmat will use for band structure calculation, one can use “split_kp.x” utility to get it. You should prepare an input file for “split_kp.x”, which can be named “gen.kpt”:

<code bash>
BAND                    # COMMENT line
20                      # number of k-points between G and M
0.000  0.000  0.000  G  # reciprocal coordinates; label 'G' for Gamma point
0.500  0.000  0.000  M
20
0.500  0.000  0.000  M
0.333  0.333  0.000  K
20
0.333  0.333  0.000  K
0.000  0.000  0.000  G
20
0.000  0.000  0.000  G
0.000  0.000  0.500  A
20
0.000  0.000  0.500  A
0.500  0.000  0.500  L
20
0.500  0.000  0.500  L
0.333  0.333  0.500  H
20
0.333  0.333  0.500  H
0.000  0.000  0.500  A
20
0.500  0.000  0.500  L
0.500  0.000  0.000  M
20
0.333  0.333  0.500  H
0.333  0.333  0.000  K
</code>

<code bash>
split_kp.x gen.kpt
</code>

After running “split_kp.x gen.kpt”, it will generate “IN.KPT” and “HIGH_SYMMETRY_POINT” (high-symmetry points information) files.

</WRAP>

Cd.SG15.PBE.SOC.UPF, Se.SG15.PBE.SOC.UPF

Spin-orbit pseudopotential files need to be used.


==== Calculations ====

  - You can submit PWmat tasks in different ways:

<code bash>
   mpirun -np 4 PWmat | tee output
</code>

<wrap round tip> Run the command directly </wrap>

<code bash>
   #!/bin/bash
   #PBS -N SCF
   #PBS -l nodes=1:ppn=4
   #PBS -q batch
   #PBS -l walltime=100:00:00

   ulimit -s unlimited
   cd $PBS_O_WORKDIR

   mpirun -np 4 PWmat | tee output
</code>

<wrap round tip> Submit the task with a pbs script </wrap>

  - After NONSCF calculation, you can run “plot_band_structure.x” to obtain band structure in your current working directory. Then it will generate the following files: bandstructure.eps, bandstructure.png, bandstructure.pdf and bandstructure_1.txt (the data file of band structure), which can be used to plot band by //origin// or //gnuplot//.

<code bash>
   plot_band_structure.x
</code>

{{:pwmat:demo:bandstructure_cdse_soc.png| pictures}}