[Wien] Error in structure file of a cubic NiTiSn generated by calLa_Pre program

[Osama Yassin]

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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