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 and the calculation of the DOS and bandstructure within 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

Cubic 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 fcc_Si, fcc_Si_DOS and fcc_Si_bandstructure, respectively.

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 (approximate) volume of 5.5 $\AA$ into the POSCAR file.

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

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

Use p4vasp or run the script dos.sh to calculate the DOS.

The example DOS should look like this:

Bandstructure

Enter (approximate) volume of 5.5 $\AA$ into the POSCAR file.

Change the INCAR according to bandstructure calculation (or use INCAR.band):

System = diamond Si
ISTART = 0 ; ICHARG=11
ENCUT  =    240
ISMEAR = 0; SIGMA = 0.1;
LORBIT = 11

Use p4vasp or run the script band.sh to calculate the bandstructure.

The example bandstructure should look like this:

For "fat" bands (or orbital character of bands) use p4vasp:

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

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

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