Ev curve

Purpose

• Generates a POSCAR file for each lattice parameter in a specified range, or, for Quantum Espresso, edits the lattice parameter in one you provide
• Executes VASP or Quantum Espresso
• Extracts energy, volume and cpu time for calculations
• Prepares data files to plot E-V curves
• Fits the E-V data to Murnaghan's equation of state and extracts equilibrium volume/lattice parameter, bulk modulus and equilibrium energy to a SUMMARY file

Usage

ev_curve fcc 3.63

The INCAR, KPOINTS, and POTCAR files must be in the same directory.

For VASP, the script should be edited with the path to your vasp executable, as well as your version of the evfit program and cleanvaspfiles script. For Quantum Espresso, you will need to provide an input script names *.ev.in, where * is the name of your structure in all lowercase.

Source

If you are using VASP:

 
#!/bin/bash

# Remove old files 
rm EvsA EvsV evfit.4 grace SUMMARY

sT="$(date +%s)"


# Set the range and number of points generated
low=`echo 0.8\*$2 | bc` 		# Sets the lower bound to 80% of guess
high=`echo 1.2\*$2 | bc`		# Sets the upper bound to 120% of guess
step=`echo "($high-$low)/20" | bc -l`	# Sets stepsize such that 20 points are created
for a in `seq -w $low $step $high`
do
echo "a= $a" 


# Lattice vectors with fewest atoms
if [ "$1" == fcc ]
then 
natom=1
cat >POSCAR <<!
Atom positions
 $a
     0.0	0.5	0.5
     0.5	0.0	0.5
     0.5	0.5	0.0
  1
Cartesian
  0.0 0.0 0.0
!

elif [ "$1" == bcc ]
then 
natom=1
cat >POSCAR <<!
Atom positions
$a
     -0.5	0.5	0.5
     0.5	-0.5	0.5
     0.5	0.5	-0.5
  1
Cartesian
  0.0 0.0 0.0
!

elif [ "$1" == hcp ]
then
natom=2
cat >POSCAR <<!
Atom positions
$a
	1.0	0.0	0.0
	-0.5	0.866	0.0
	0.0	0.0	1.633
 2
Cartesian
	0.0 	0.0 	0.0
	0.0	0.57735	0.8165
!

fi

# Run VASP with the new POSCAR file
# Must provide path to executable
mpirun -np 4 vasp

# Gather energy and volume data from the VASP outputs
# Store the data in "EvsA" and "EvsV" text files
V=`grep volume/ion OUTCAR|awk '{print $5}'`
E=`tail -n1 OSZICAR | awk '{ print $5/1}'`
E=`echo "$E/$natom" | bc -l`
echo $a $E >> EvsA
echo $V $E >> EvsV

# Clean up VASP files
./cleanvaspfiles

# Restart
done


# Once VASP has been run for each lattice parameter in the range
# Run evfit routine with equation of state 4
cat <<! | ./evfit
$1
4
EvsA
evfit.4
!

# Gather data from evfit output
Emin=`grep Emin evfit.4|awk '{print $2}'`
A0=`grep A0 evfit.4|awk '{print $2}'`
K0=`grep A0 evfit.4|awk '{print $4}'`

# Put that data in an output file called "SUMMARY"
totT="$(($(date +%s)-sT))"
tail +5 evfit.4|awk '{print $1,"\t", $2,"\t", $3}' > grace

echo "Data for $1" >> SUMMARY
echo "=================================================" >> SUMMARY
echo "Equilibrium Energy per Atom    = $Emin">>SUMMARY
echo "Equilibrium lattice constant   = $A0">>SUMMARY
echo "Bulk Modulus                   = $K0">>SUMMARY
echo "Total RUN time (sec)           = $totT">>SUMMARY

If you are using Quantum Espresso:

#!/bin/bash
# usage: ev_curve <structure> <alat_guess>
# ev_curve fcc 3.61
# 
# The script also requires input scripts for each structure named as follows:
# fcc.ev.in
# bcc.ev.in
# hcp.ev.in
# These scripts will define the pseudopotential, structure, and calculation parameters

# Remove old files 
rm EvsA EvsV evfit.4 SUMMARY

sT="$(date +%s)"

# Set the range and number of points generated
low=`echo 0.8\*$2 | bc` 		# Sets the lower bound to 80% of guess
high=`echo 1.2\*$2 | bc`		# Sets the upper bound to 120% of guess
step=`echo "($high-$low)/20" | bc -l`	# Sets stepsize such that 20 points are created
for a in `seq -w $low $step $high`
do
#a=2.9
echo "a= $a" 
a_au=`echo "$a/0.529" | bc -l`

# Lattice vectors with fewest atoms
if [ "$1" == fcc ] || [ "$1" == bcc ]
then 
natom=1

elif [ "$1" == hcp ]
then
natom=2

fi

input=$1.ev.in
 
# sed the lattice parameter
curr=`grep "celldm(1)" $input | awk '{print $4}'`
sed -i "s/celldm(1) $curr/celldm(1) =$a_au,/g" $input

# Run Quantum Espresso with the correct input deck
# Must provide path to executable
pw.x < $input > pw_ev.out

# Gather energy and volume data from the output file
# Store the data in "EvsA" and "EvsV" text files
V=`grep volume pw_ev.out | awk '{print $4}'`
E=`grep "! *[ ] total energy" pw_ev.out | awk '{print $5}'`
# Convert volume to Ang^3 and energy to eV
V=`echo "$V*0.1481847" | bc -l`
E=`echo "$E/$natom*13.605685" | bc -l`
echo $a $E >> EvsA
echo $V $E >> EvsV

# Restart
done

# Once VASP has been run for each lattice parameter in the range
# Run evfit routine with equation of state 4
cat <<! | ./evfit
$1
4
EvsA
evfit.4
!

# Gather data from evfit output
Emin=`grep Emin evfit.4|awk '{print $2}'`
A0=`grep A0 evfit.4|awk '{print $2}'`
K0=`grep A0 evfit.4|awk '{print $4}'`

# Put that data in an output file called "SUMMARY"
totT="$(($(date +%s)-sT))"

echo "Data for $1" >> SUMMARY
echo "=================================================" >> SUMMARY
echo "Equilibrium Energy per Atom    = $Emin">>SUMMARY
echo "Equilibrium lattice constant   = $A0">>SUMMARY
echo "Bulk Modulus                   = $K0">>SUMMARY
echo "Total RUN time (sec)           = $totT">>SUMMARY