Fcc Si: Difference between revisions

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Description: the bash-script <tt>loop.sh</tt> runs fcc Si at several different lattice constants (3.5-4.3 Å) and collects free energy versus lattice constant into the file SUMMARY.fcc
{{Template:Bulk_systems - Tutorial}}


To make a quick plot of SUMMARY.fcc try:
== Task ==


gnuplot
Lattice constant optimization for fcc Si.
gnuplot> plot "SUMMARY.fcc" using ($1):($4) w lp


----
== Input ==
*INCAR
System = fcc Si
ISTART = 0 ; ICHARG=2
ENCUT  =   240
ISMEAR = 0; SIGMA = 0.1


*KPOINTS
=== {{TAG|POSCAR}} ===
k-points
  0
Monkhorst Pack
  11 11 11
  0  0  0
 
*POSCAR
  fcc Si:
  fcc Si:
   3.9
   3.9
Line 30: Line 17:
  0 0 0
  0 0 0


*And a simple bash-script to loop over several lattice constants: loop.sh
*Fcc Si lattice constant of 3.9 <math>\AA</math>.
#! /bin/bash
*1 atom per unit cell.
BIN=/path/to/your/vasp/executable
 
rm WAVECAR SUMMARY.fcc
=== {{TAG|INCAR}} ===
for i in  3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2 4.3 ; do
{{TAGBL|System}} = fcc Si
cat >POSCAR <<!
{{TAGBL|ISTART}} = 0 ; {{TAGBL|ICHARG}} = 2
fcc:
{{TAGBL|ENCUT}} = 240
    $i
{{TAGBL|ISMEAR}} = 0; {{TAGBL|SIGMA}} = 0.1
  0.5 0.5 0.0
 
  0.0 0.5 0.5
*Initial charge density form overlapping atoms.
  0.5 0.0 0.5
*Energy cutoff of 240 eV from {{TAG|POTCAR}} file.
    1
 
cartesian
=== {{TAG|KPOINTS}} ===
0 0 0
k-points
!
  0
echo "a= $i" ; mpirun -np 2 $BIN
Monkhorst Pack
E=`awk '/F=/ {print $0}' OSZICAR` ; echo $i $E  >>SUMMARY.fcc
  11 11 11
  done
  0  0  0
  cat SUMMARY.fcc
 
*Equally spaced k mesh.
*Odd number of k points in each direction results in a <math>\Gamma</math> centered mesh.
*56 k points in IBZ.
 
== Calculation ==
 
*Calculate energy for different lattice parameters.
*Fit to some equation of states to obtain the equilibrium volume.
 
*The bash-script <tt>loop.sh</tt> runs fcc Si at several different lattice constants (3.5-4.3 &Aring;) and collects free energy versus lattice constant into the file SUMMARY.fcc
<pre>
#! /bin/bash
BIN=/path/to/your/vasp/executable
rm WAVECAR SUMMARY.fcc
for i in  3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2 4.3 ; do
cat >POSCAR <<!
fcc:
  $i
0.5 0.5 0.0
0.0 0.5 0.5
0.5 0.0 0.5
  1
cartesian
0 0 0
!
echo "a= $i" ; mpirun -np 2 $BIN
E=`awk '/F=/ {print $0}' OSZICAR` ; echo $i $E  >>SUMMARY.fcc
done
cat SUMMARY.fcc
</pre>
 
The output for the SUMMARY.fcc file within this example should look like this:
 
  3.5 1 F= -.44256712E+01 E0= -.44233993E+01 d E =-.454388E-02
3.6 1 F= -.46614699E+01 E0= -.46600410E+01 d E =-.285796E-02
3.7 1 F= -.47979864E+01 E0= -.47959298E+01 d E =-.411323E-02
3.8 1 F= -.48645042E+01 E0= -.48630063E+01 d E =-.299564E-02
3.9 1 F= -.48773847E+01 E0= -.48758538E+01 d E =-.306176E-02
4.0 1 F= -.48487436E+01 E0= -.48481092E+01 d E =-.126878E-02
4.1 1 F= -.47852634E+01 E0= -.47844854E+01 d E =-.155599E-02
4.2 1 F= -.46936947E+01 E0= -.46922530E+01 d E =-.288339E-02
4.3 1 F= -.45831167E+01 E0= -.45811837E+01 d E =-.386598E-02
 
*To make a quick plot of SUMMARY.fcc try:
 
gnuplot
  gnuplot> plot "SUMMARY.fcc" using ($1):($4) w lp
 
*The equilibrium lattice constant is found at roughly 3.9 &Aring;. Adjust your {{TAG|POSCAR}} file to reflect this and rerun VASP.
 
*Keep your {{TAG|CHGCAR}} file from this run. We will need it in the following examples.
 
*A quick look at the results:
[[File:Fig Si 1.png|800px]]


'''Mind''': You will have to set the correct path to your VASP executable (i.e., <tt>BIN</tt>), and invoke VASP with the correct command (e.g., in the above: <tt>mpirun -np 2</tt>).
'''Mind''': You will have to set the correct path to your VASP executable (i.e., <tt>BIN</tt>), and invoke VASP with the correct command (e.g., in the above: <tt>mpirun -np 2</tt>).
 
== Download ==
== Download ==
[http://www.vasp.at/vasp-workshop/examples/name.tgz name.tgz]
[[Media:FccSi.tgz| fccSi.tgz]]


----
{{Template:Bulk_systems}}
[[VASP_example_calculations|To the list of examples]] or to the [[The_VASP_Manual|main page]]


[[Category:Examples]]
[[Category:Examples]]

Latest revision as of 13:24, 14 November 2019

Task

Lattice constant optimization for fcc Si.

Input

POSCAR

fcc Si:
 3.9
 0.5 0.5 0.0
 0.0 0.5 0.5
 0.5 0.0 0.5
   1
cartesian
0 0 0
  • Fcc Si lattice constant of 3.9 .
  • 1 atom per unit cell.

INCAR

System = fcc Si
ISTART = 0 ; ICHARG = 2
ENCUT = 240
ISMEAR = 0; SIGMA = 0.1
  • Initial charge density form overlapping atoms.
  • Energy cutoff of 240 eV from POTCAR file.

KPOINTS

k-points
 0
Monkhorst Pack
 11 11 11
 0  0  0
  • Equally spaced k mesh.
  • Odd number of k points in each direction results in a centered mesh.
  • 56 k points in IBZ.

Calculation

  • Calculate energy for different lattice parameters.
  • Fit to some equation of states to obtain the equilibrium volume.
  • The bash-script loop.sh runs fcc Si at several different lattice constants (3.5-4.3 Å) and collects free energy versus lattice constant into the file SUMMARY.fcc
#! /bin/bash
BIN=/path/to/your/vasp/executable
rm WAVECAR SUMMARY.fcc
for i in  3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2 4.3 ; do
cat >POSCAR <<!
fcc:
   $i
 0.5 0.5 0.0
 0.0 0.5 0.5
 0.5 0.0 0.5
   1
cartesian
0 0 0
!
echo "a= $i" ; mpirun -np 2 $BIN
E=`awk '/F=/ {print $0}' OSZICAR` ; echo $i $E  >>SUMMARY.fcc
done
cat SUMMARY.fcc

The output for the SUMMARY.fcc file within this example should look like this:

3.5 1 F= -.44256712E+01 E0= -.44233993E+01 d E =-.454388E-02
3.6 1 F= -.46614699E+01 E0= -.46600410E+01 d E =-.285796E-02
3.7 1 F= -.47979864E+01 E0= -.47959298E+01 d E =-.411323E-02
3.8 1 F= -.48645042E+01 E0= -.48630063E+01 d E =-.299564E-02
3.9 1 F= -.48773847E+01 E0= -.48758538E+01 d E =-.306176E-02
4.0 1 F= -.48487436E+01 E0= -.48481092E+01 d E =-.126878E-02
4.1 1 F= -.47852634E+01 E0= -.47844854E+01 d E =-.155599E-02
4.2 1 F= -.46936947E+01 E0= -.46922530E+01 d E =-.288339E-02
4.3 1 F= -.45831167E+01 E0= -.45811837E+01 d E =-.386598E-02
  • To make a quick plot of SUMMARY.fcc try:
gnuplot
gnuplot> plot "SUMMARY.fcc" using ($1):($4) w lp
  • The equilibrium lattice constant is found at roughly 3.9 Å. Adjust your POSCAR file to reflect this and rerun VASP.
  • Keep your CHGCAR file from this run. We will need it in the following examples.
  • A quick look at the results:

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

fccSi.tgz