Dear Siesta users,
can you please help me with with Postnikov's tool: Murnaghan equation of
state fit.
I calculated Etot(alat) for several alat for GaSb (zincblende structure)
using fdf file as below (important part is shown):
LatticeConstant 6.12 Ang
%block LatticeVectors
0.000 0.500 0.500
0.500 0.000 0.500
0.500 0.500 0.000
%endblock LatticeVectors
NumberOfAtoms 2
NumberOfSpecies 2
%block ChemicalSpeciesLabel
1 31 Ga-3d
2 51 Sb
%endblock ChemicalSpeciesLabel
AtomicCoordinatesFormat ScaledCartesian
%block AtomicCoordinatesAndAtomicSpecies
0.000 0.000 0.000 1 # Ga 1
0.250 0.250 0.250 2 # Sb 2
%endblock AtomicCoordinatesAndAtomicSpecies
The generated values are:
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
Then I translated Ang units to atomic units and eV to Rydbergs as requested
by Postnikov's tool: Murnaghan equation of state. Then set Volume=alat^3.
The output from this tool contains:
# Equilibrium volume, a.u.^3 : 602.102908
# Minimum energy, Ry : -145.201385
# Bulk modulus, Kbar : 47.134730
The values are seriously wrong since for GaSb
GaSb zincblende a=6.09593 Ang, B=57.0 GPa
What I am doing wrong?
Ruslan
