Cd Si

Overview > fcc Si > fcc Si DOS > fcc Si bandstructure > cd Si > cd Si volume relaxation > cd Si relaxation > beta-tin Si > fcc Ni > graphite TS binding energy > graphite MBD binding energy  > graphite interlayer distance  > List of tutorials

Task

Volume relaxtion of cubic diamond (cd) Si and the calculation of the DOS and bandstructure.

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 $\AA$.
• 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 calculation of the optimized volume. DOS and bandstructure is similar as in the examples for fcc Si (

Volume relaxation

• 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 $\AA$.

DOS

• Enter correct volume of 5.5 $\AA$ into the POSCAR file.

• Change the INCAR to DOS calculation (or use INCAR.dos):

System = diamond Si
ISTART = 0 ; ICHARG=2
ENCUT  =    240
ISMEAR = -5
LORBIT = 11

• The script dos.sh calculates the DOS.

Bandstructure

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).

Download

diamondSi.tgz

---

To the list of examples or to the main page