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====== Bandsctructure calculation ======

Bandstructure calculation for Si

===== Input files =====

atom.config

<code bash>
        2
 LATTICE
      0.00000000     2.71535000     2.71535000
      2.71535000     0.00000000     2.71535000
      2.71535000     2.71535000     0.00000000
 POSITION
  14     0.00000000     0.00000000     0.00000000 0 0 0
  14     0.25000000     0.25000000     0.25000000 0 0 0
</code>

===== etot.input =====

<code bash>
   1 4
   JOB = NONSCF
   IN.PSP1 = Si.SG15.PBE.UPF
   IN.ATOM = atom.config
   ECUT = 50
   IN.VR = T
   IN.KPT = T
</code>

<note>

  - Read IN.VR from previous SCF calculation. To copy OUT.VR and OUT.FERMI from the SCF calculation of example [[scf|Si 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
      10                      # number of k-points between X and R
      0.500  0.000  0.000  X  # reciprocal coordinates; label 'X' for X point
      0.500  0.500  0.500  R
      10
      0.500  0.500  0.500  R
      0.500  0.500  0.000  M
      10
      0.500  0.500  0.000  M
      0.000  0.000  0.000  G
      10
      0.000  0.000  0.000  G
      0.500  0.500  0.500  R
</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.
</note>

Si.SG15.PBE.UPF

Si.SG15.PEB.UPF is the pseudopotential file.


===== Calculations =====

  - You can submit PWmat tasks in different ways:

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

<note>
Run the command directly
</note>


----

<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>

<note>
Submit the task with a pbs script 
</note>

  - 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//. Note, for “spin=2”, another data file bandstructure_2.txt will be generated.

<code bash>
   plot_band_structure.x
</code>

{{:pwmat:demo:bandstructure.png|band}}

===== Download =====

[[http://doc.lonxun.com/Examples/examples/Si_Band_Cal.tar.gz|Si_Band_Cal]]