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

[Peter Blaha]

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
> 
> 
> Sent from Outlook <http://aka.ms/weboutlook>
> 
> 
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-- 

                                       P.Blaha
--------------------------------------------------------------------------
Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-165300             FAX: +43-1-58801-165982
Email: blaha at theochem.tuwien.ac.at    WIEN2k: http://www.wien2k.at
WWW:   http://www.imc.tuwien.ac.at/TC_Blaha
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