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Thirdorder 计算

已有 5774 次阅读 2018-1-16 14:56 |个人分类:Phonons|系统分类:科研笔记

#Running thirdorder with VASP #

1. Prepare input files for vasp calculations.

Any invocation of thirdorder_vasp.py requires a POSCAR file with a description of the unit cell to be present in the current directory. The script uses no other configuration files, and takes exactly five mandatory command-line arguments:

```bash

thirdorder_vasp.py sow|reap na nb nc cutoff [nm/-integer]

```

sow|reap                 ! displacement generation or IFC matrix reconstruction

na nb nc                  ! specify the dimensions of the supercell to be created

cutoff[nm/-integer] ! a force cutoff distance. Positive: a distance in nm; Negative -n: n-th neighbors is automatically

```bash

thirdorder_vasp.py sow 4 4 4 -3

```

2. Self-consistent calculation of vasp.

```bash
for i in 3RD.POSCAR.*;do
  s=$(echo $i|cut -d"." -f3) &&
  d=job-$s &&
  mkdir $d &&
  cp $i $d/POSCAR &&
  cp ~/vaspinputs/INCAR ~/vaspinputs/POTCAR ~/vaspinputs/KPOINTS $d&&
  cp ~/vaspinputs/runvasp.sh $d &&
  (cd $d && qsub runvasp.sh)
done
```

3. post-process vasprun.xml files.

Some time later, after all these jobs have finished successfully, we only need to feed all the vasprun.xml files in the right order to thirdorder_vasp.py, this time in reap mode:

```bash

find job* -name vasprun.xml|sort -n|thirdorder_vasp.py reap 4 4 4 -3

```

If everything goes according to plan, a FORCE_CONSTANTS_3RD file will be created at the end of this run. Naturally, it is important to choose the same parameters for the sow and reap steps.



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