[Wien] another space group question : hexagonal to orthorhombic

[Gilles Hug]

Hi,
After having recompile the latest archive the situation has improved.
I have now 0.02467 Ryd difference in total energy. I can probably live  
with that.
Is that ok ?
The only difference I can see is the sampling of kpoints which may be  
chosen at different positions in both structure.
Is it possible(/useful) to constrain the kpoints to be exactly the same  
in the hexagonal and orthorhombic structure?
Thanks for advise
Gilles

Le 22 janv. 04, à 10:05, Peter Blaha a écrit :

> DO you use the latest version of LAPW0 ? I think I even announced this  
> bugfix
> on the mailing list. Have a look at    
> http://www.wien2k.at/reg_user/updates
>
> # 26.11.2003: SRC_lapw0/latgen.f: Fix of a serious bug for  
> GGA-calculations for CXY lattices.
>
>
>> In order to make deformations, I have built an orthorhombic structure
>> file (#63 Cmcm) which is equivalent to an hexagonal one (#194  
>> P63/mmc).
>> The orthorhombic cell has double volume and is centered. The hex cell
>> basis is (a, b=a, c) and the ortho (a, a+2b, c)/
>> I have extensively checked both structures and can't find difference.
>> They both have same volume, atoms are in same positions and all other
>> parameters are identical (kpts, RMT, RKM,...).
>> In both cases the calculation runs smoothly.
>> However I get 0.1 Ryd difference in total energy between the two
>> structures, which seems to me way too large.
>> I am puzzled.
>
>
>                                       P.Blaha
> ----------------------------------------------------------------------- 
> ---
> Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
> Phone: +43-1-58801-15671             FAX: +43-1-58801-15698
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> http://info.tuwien.ac.at/theochem/
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Dr. Gilles Hug
LEM ONERA-CNRS
BP 72
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+33 1 46 73 45 42
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