I've never used calLa_Pre.
Apparently your lattice has fcc structure and this program does not take
this into account.
It is either a programming error or an improper use of the program.
PS: Take the volume which calLa_Pre prints (352.8832 for 1 GPa),
multiply by four and take the cube-root.
Sometimes problems are so difficult ...
On 03/23/2018 08:02 AM, Osama Yassin wrote:
Dear Wien2k developers and users
I have optimized the lattice geometry of a cubic NiTiSn half-Heusler
alloys by using both BPE-GGA and SCAN functionals.
After obtaining the EOS I had generated structure files at different
pressure values in the range from 1 to 15 GPa.
The generated lattice constant is so small and thus an error appears
with nn execution (unphysical rmt value).
Here is the output of the lattice optimization done by Wien2k v17.1
Equation of state: EOS2 (PRB52,8064) info 2
a,b,c,d -17137.653776 734.841266 -5894.224839 15544.779981
V0,B(GPa),BP,E0 355.6656 125.8716 6.1900
cubic lattice parameter: 11.2469 bohr = 5.9516 Ang
Equation of state: Murnaghan info 7
E=E0+[B*V/BP*(1/(BP-1)*(V0/V)**BP +1)-B*V0/(BP-1)]/14703.6
Pressure=B/BP*((V0/V)**BP -1)
V0,B(GPa),BP,E0 355.6503 124.9491 6.2049 -17107.648797
cubic lattice parameter: 11.2468 bohr = 5.9515 Ang
vol energy de(EOS2) de(Murnaghan) Pressure(GPa)
338.8098 -17107.645076 0.000111 0.000093 7.072
328.2219 -17107.637809 -0.000037 -0.000029 12.997
352.9268 -17107.648746 0.000036 0.000040 0.984
354.6915 -17107.648662 -0.000128 -0.000124 0.340
356.4561 -17107.648672 -0.000122 -0.000117 -0.281
367.0439 -17107.647560 0.000203 0.000203 -3.579
377.6317 -17107.643718 -0.000063 -0.000066 -6.257
Sigma: 0.000114 0.000111
The output of the calLa_Pre for 1 GPa pressure is
V0,B(GPa),BP 355.6503 124.9491 6.2049
11.217986 11.217986 11.217986 90.000000 90.000000 90.000000
new Volume,Cof,b/a ratio,c/a ratio -----> 352.8832 0.250000
1.000000 1.000000
new a,b,c -----> 7.066597 7.066597 7.066597
As it can be seen from the result of the lattice optimization a pressure
of 12.997 GPa is applicable to this structure.
My question why the lattice generated by calLa_Pre is so small for this
structure at 1 GPa?.
O A Yassin
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