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}}


----
== Task ==
*{{TAG|INCAR}}
System = fcc Si
ISTART = 0 ; ICHARG=2
ENCUT  =   240
ISMEAR = 0; SIGMA = 0.1


*{{TAG|KPOINTS}}
Lattice constant optimization for fcc Si.
k-points
 
  0
== Input ==
Monkhorst Pack
  11 11 11
  0  0  0


*{{TAG|POSCAR}}
=== {{TAG|POSCAR}} ===
  fcc Si:
  fcc Si:
   3.9
   3.9
Line 25: 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>.
*1 atom per unit cell.
 
=== {{TAG|INCAR}} ===
{{TAGBL|System}} = fcc Si
{{TAGBL|ISTART}} = 0 ; {{TAGBL|ICHARG}} = 2
{{TAGBL|ENCUT}} = 240
{{TAGBL|ISMEAR}} = 0; {{TAGBL|SIGMA}} = 0.1
 
*Initial charge density form overlapping atoms.
*Energy cutoff of 240 eV from {{TAG|POTCAR}} file.
 
=== {{TAG|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 <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>
<pre>
#! /bin/bash
#! /bin/bash
Line 47: Line 67:
</pre>
</pre>


'''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>).
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:
*To make a quick plot of SUMMARY.fcc try:
Line 54: Line 84:
  gnuplot> plot "SUMMARY.fcc" using ($1):($4) w lp
  gnuplot> plot "SUMMARY.fcc" using ($1):($4) w lp


== Used INCAR Tags ==
*The equilibrium lattice constant is found at roughly 3.9 &Aring;. Adjust your {{TAG|POSCAR}} file to reflect this and rerun VASP.
{{TAG|ENCUT}}, {{TAG|ICHARG}}, {{TAG|ISMEAR}}, {{TAG|ISTART}}, {{TAG|SIGMA}}, {{TAG|SYSTEM}}
 
*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>).


== Download ==
== Download ==
[http://www.vasp.at/vasp-workshop/examples/fccSi.tgz fccSi.tgz]
[[Media:FccSi.tgz| fccSi.tgz]]
----
 
[[VASP_example_calculations|To the list of examples]] or to the [[The_VASP_Manual|main page]]
{{Template:Bulk_systems}}


[[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