[Wien] another space group question : hexagonal to orthorhombic

[Jorissen Kevin]

I'd say it's not okay.
Even if k space sampling is somewhat different, these differences should disappear for large k-meshes.
Sadly, I cannot offer you any suggestion as to what is the problem here.
 
Kevin.
 

	-----Oorspronkelijk bericht----- 
	Van: Gilles Hug [mailto:gilles.hug at onera.fr] 
	Verzonden: vr 1/30/2004 6:34 
	Aan: wien at zeus.theochem.tuwien.ac.at 
	CC: 
	Onderwerp: Re: [Wien] another space group question : hexagonal to orthorhombic
	
	

	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
	> Email: blaha at theochem.tuwien.ac.at    WWW: 
	> http://info.tuwien.ac.at/theochem/
	> -----------------------------------------------------------------------
	> ---
	>
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	>
	>
	Dr. Gilles Hug
	LEM ONERA-CNRS
	BP 72
	92322 Châtillon
	France
	+33 1 46 73 45 42
	gilles.hug at onera.fr
	
	
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