cd Si relaxation

cubic diamond Si relaxation

Based on the VASP wiki example in this link

Task: Relaxation of the internal coordinates of a perturbed cubic diamond Si structure.

First, copy the example folder which contains some of the VASP input files and useful scripts

cp -r /software/sse/manual/vasp/training/ws2020/cd_Si_relax .
cd cd_Si_relax

and copy the latest POTCAR file for Si:

cp /software/sse/manual/vasp/POTCARs/PBE/2015-09-21/Si/POTCAR .

Input files

POSCAR

cubic diamond Si
   5.5
 0.0    0.5     0.5
 0.5    0.0     0.5
 0.5    0.5     0.0
Si 
  2
Direct
 -0.125 -0.125 -0.125
  0.125  0.125  0.130

Note the distortion for the 2nd atom in z, from 0.125 to 0.130

INCAR

System = diamond Si

ISTART = 0
ICHARG=2
ENCUT  =    240
ISMEAR = 0 
SIGMA = 0.1
NSW    =  10 
IBRION =  2
ISIF   =  2
EDIFFG = -0.0001

NSW=10 relaxation steps
IBRION=2, conjugate-gradient algorithm
ISIF=2, relax only internal parameters

KPOINTS

k-points
 0
Monkhorst Pack
 11 11 11
 0  0  0

Calculation

The input files are ready for the atom relaxation, so the job can be started directly

sbatch run.sh

Check the progress of the relaxation by e.g.

cat slurm*out
cat OSZICAR

the calculation should be quite fast. At the end of OUTCAR, e.g. using less, check the final forces

 POSITION                                       TOTAL-FORCE (eV/Angst)
 -----------------------------------------------------------------------------------
      4.81938      4.81938      4.81254        -0.000143     -0.000143     -0.001100
      0.69437      0.69437      0.68746         0.000143      0.000143      0.001100
 -----------------------------------------------------------------------------------
    total drift:                                0.000001      0.000001     -0.000003

The resulting structure can be found in CONTCAR
The progress of the structure at each relaxation point is found in XDATCAR

cubic diamond Si relaxation

Input files

Calculation

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