About equilibrium volume, which scheme is more reasonable?
Posted: Thu Aug 18, 2011 11:03 pm
taking bccFe for example.
Scheme 1. A set of static calculations, scannig volumes. ISMEMR=-5
Then fit Birch-Murnaghan EOS to get the equilibrium volume (or lattice constant)
Using the equilibrium lattice constant to do another static run.
INCAR
job script
Scheme 2: same with Scheme 1, except that ISMEAR=1
Scheme 3: Using relaxation
INCAR
(a) run vasp the first time
(b) cp CONTCAR POSCAR
and run vasp another time
(c) cp CONTCAR POSCAR
and remove "####" lines to do one more static calcultion
Scheme 4. same with Scheme 1, except that ISMEAR=1
At last, I get lattice constant a and pressure P as follow:
Scheme 1: a=2.3847, P=-5.07kB
Scheme 2: a=2.3828, P=-0.21kB
Scheme 3: after step (a) a=2.7229, P=-0.47kB
after step (b) a=2.8247, P=-1.51kB
after step (c) P=15.47kB
Scheme 4: after step (a) a=2.7665, P=1.18kB
after step (b) a=2.8293, P=0.72kB
after step (c) P=7.72kB
Now, I want to wihch result is more reasonable?
<span class='smallblacktext'>[ Edited ]</span>
Scheme 1. A set of static calculations, scannig volumes. ISMEMR=-5
Then fit Birch-Murnaghan EOS to get the equilibrium volume (or lattice constant)
Using the equilibrium lattice constant to do another static run.
INCAR
Code: Select all
ISTART =0
ICHARG =2
EDIFF =1e-6
ISPIN =2
MAGMOM=3
PREC =High
ENCUT =300
ISMEAR =-5
job script
Code: Select all
#!/usr/bin/env bash
echo -n > E_vol
for i in 2.70 2.77 2.82 2.87 2.95 2.97 3.04
do
cat <<EOF >POSCAR
bccFe
$i
-0.5 0.5 0.5
0.5 -0.5 0.5
0.5 0.5 -0.5
1
Direct
0 0 0
EOF
echo ==========a=$i============
vasp
E=$(tail -1 OSZICAR)
echo "$i $E" >> E_vol
done
Scheme 2: same with Scheme 1, except that ISMEAR=1
Scheme 3: Using relaxation
INCAR
Code: Select all
ISTART =0
ICHARG =2
EDIFF =1e-6
ISPIN =2
MAGMOM=3
PREC =High
ENCUT =300
ISMEAR =-5
IBRION=2 ####
ISIF=7 ####
NSW=20 ####
(a) run vasp the first time
(b) cp CONTCAR POSCAR
and run vasp another time
(c) cp CONTCAR POSCAR
and remove "####" lines to do one more static calcultion
Scheme 4. same with Scheme 1, except that ISMEAR=1
At last, I get lattice constant a and pressure P as follow:
Scheme 1: a=2.3847, P=-5.07kB
Scheme 2: a=2.3828, P=-0.21kB
Scheme 3: after step (a) a=2.7229, P=-0.47kB
after step (b) a=2.8247, P=-1.51kB
after step (c) P=15.47kB
Scheme 4: after step (a) a=2.7665, P=1.18kB
after step (b) a=2.8293, P=0.72kB
after step (c) P=7.72kB
Now, I want to wihch result is more reasonable?
<span class='smallblacktext'>[ Edited ]</span>