Hi,
Alexander Vozny wrote:
alat (Ang) Etot (eV)
------------------------------
6.12 -1975.526018
6.14 -1975.531451
6.16 -1975.535169
6.18 -1975.53714
6.20 -1975.537384
6.22 -1975.535722
6.24 -1975.5324
6.26 -1975.527514
Your a is somewhere around 6.19
# Equilibrium volume, a.u.^3 : 602.102908
which gives a=8.44a0=4.46A
Andrei's tool cannot make such an error, so I'd expect that you
converted to atomic units incorrectly.
# Bulk modulus, Kbar : 47.134730
GaSb zincblende a=6.09593 Ang, B=57.0 GPa
It is typical for bulk modulus to be about 10% off expt value, plus or
minus depends on GGA or LDA. (But since the lattice constant is wrong
then this number is not correct anyhow).
i'm getting the following with ase's eos.py (script attached):
eos v0(eV**3) e0(eV) B0(GPa) a0(A)
poly 237.421 -1975.537445 12.55 6.192
taylor 237.471 -1975.537444 12.50 6.193
murnaghan 237.414 -1975.537443 12.56 6.192
birch 237.414 -1975.537443 12.56 6.192
birchmurnaghan 237.413 -1975.537443 12.54 6.192
pouriertarantola 237.413 -1975.537442 12.55 6.192
vinet 237.414 -1975.537443 12.56 6.192
Marcin
alats = [
6.12,
6.14,
6.16,
6.18,
6.20,
6.22,
6.24,
6.26,
]
volumes = [a**3 for a in alats]
energies = [
-1975.526018,
-1975.531451,
-1975.535169,
-1975.53714,
-1975.537384,
-1975.535722,
-1975.5324,
-1975.527514,
]
from eos import EquationOfState
from eos import GPa
print 'eos v0(eV**3) e0(eV) B0(GPa) a0(A)'
for eos_type in [
'poly',
'taylor', 'murnaghan',
'birch', 'birchmurnaghan', 'pouriertarantola',
'vinet',
#'antonschmidt' # probably broken?
]:
eos = EquationOfState(volumes, energies, eos=eos_type)
v0, e0, B0 = eos.fit()
print "%16s %.3f %.6f %.2f %.3f" % (eos_type, round(v0, 3), round(e0, 6), round(B0/GPa, 2), round(v0**(1./3), 3))
#eos.plot()
