Cd Si
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Task
Volume relaxtion of cubic diamond (cd) Si.
Input
POSCAR
cubic diamond 5.5 0.0 0.5 0.5 0.5 0.0 0.5 0.5 0.5 0.0 2 Direct -0.125 -0.125 -0.125 0.125 0.125 0.125
- Diamond Si starting lattice constant of 5.5 .
- Fcc cell.
- 2 atoms in cell.
INCAR
System = diamond Si ISTART = 0 ; ICHARG=2 ENCUT = 240 ISMEAR = 0; SIGMA = 0.1
KPOINTS
k-points 0 Monkhorst Pack 11 11 11 0 0 0
Calculation
- The bash-script loop.sh runs Si in the cubic diamond (cd) structure at several different lattice constants (5.1-5.7 Å) and collects free energy versus lattice constant into the file SUMMARY.dia:
#! /bin/bash
BIN=/path/to/your/vasp/executable
rm WAVECAR SUMMARY.dia
for i in 5.1 5.2 5.3 5.4 5.5 5.6 5.7 ; do
cat >POSCAR <<!
cubic diamond
$i
0.0 0.5 0.5
0.5 0.0 0.5
0.5 0.5 0.0
2
Direct
-0.125 -0.125 -0.125
0.125 0.125 0.125
!
echo "a= $i" ; mpirun -n 2 $BIN
E=`awk '/F=/ {print $0}' OSZICAR` ; echo $i $E >>SUMMARY.dia
done
cat SUMMARY.dia
- Example output of SUMMARY.dia:
5.2 1 F= -.10528151E+02 E0= -.10528137E+02 d E =-.274709E-04 5.3 1 F= -.10713281E+02 E0= -.10713280E+02 d E =-.218410E-05 5.4 1 F= -.10806685E+02 E0= -.10806685E+02 d E =-.114401E-06 5.5 1 F= -.10823039E+02 E0= -.10823039E+02 d E =-.429842E-08 5.6 1 F= -.10775102E+02 E0= -.10775102E+02 d E =-.204668E-09 5.7 1 F= -.10673578E+02 E0= -.10673578E+02 d E =-.112715E-10 5.8 1 F= -.10528393E+02 E0= -.10528393E+02 d E =-.552513E-11
- To make a quick plot of SUMMARY.dia try:
gnuplot gnuplot> plot "SUMMARY.dia" using ($1):($4) w lp
- Extracted lattice parameter should be at 5.465 .
Mind: You will have to set the correct path to your VASP executable (i.e., BIN), and invoke VASP with the correct command (e.g., in the above: mpirun -np 2).
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