[Wien] Whether there would be energy difference between k point sampling via 2x2x3 & 3x2x2?

[Peter Blaha]

Very basic solid state theory:

k-space has NOTHING to do with atoms ....

It is connected with the   reciprocal lattice  (what the hell is this ??)

Anyway, if direct space (unit cell dimension) is large in one direction, 
reciprocal space is small. To sample k-space, you need many points when 
the reciprocal lattice vector is large (i.e. direct space is short) and 
vice versa.

Obviously, if a and b axes of a lattice have equal length, you have to 
use the same number of points in these 2 directions in k-space. 
Otherwise, you should use a k-mesh ratio, which is inversely 
proportional to the unit cell length.

And finally:   why are you choosing your k-mesh yourself by this 
dangerous method of specifying 3 numbers, if you have no idea what you 
are doing. Use the suggestions of WIEN2k_22 during initialization with a 
certain precision and the metal/nometal option.

Am 25.08.2023 um 11:53 schrieb shamik chakrabarti:
> Dear Sir,
> 
>              Should I keep 3x2x2 for a structure having less atoms along 
> y & z -direction in comparison to x-direction?
> 
> On Fri, 25 Aug 2023 at 20:46, Peter Blaha <peter.blaha at tuwien.ac.at 
> <mailto:peter.blaha at tuwien.ac.at>> wrote:
> 
>     Did you do the calculations ? Then you know the answer.
> 
>     All what we can say without details: One of the choices is for sure
>     wrong.
> 
>     Am 25.08.2023 um 07:15 schrieb shamik chakrabarti:
>      > Dear Wien2k users,
>      >
>      >                           I have a basic question.
>      > Whether there would be energy difference between k point sampling
>     via
>      > 2x2x3 & 3x2x2?
>      >
>      > Looking forward to your reply.
>      >
>      > witty regards,
>      > --
>      > Dr. Shamik Chakrabarti
>      > Research Fellow
>      > Department of Physics
>      > Indian Institute of Technology Patna
>      > Bihta-801103
>      > Patna
>      > Bihar, India
>      >
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>     -- 
>     --------------------------------------------------------------------------
>     Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
>     Phone: +43-1-58801-165300
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> 
> 
> 
> -- 
> Dr. Shamik Chakrabarti
> Research Fellow
> Department of Physics
> Indian Institute of Technology Patna
> Bihta-801103
> Patna
> Bihar, India
> 
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-- 
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-165300
Email: peter.blaha at tuwien.ac.at    WIEN2k: http://www.wien2k.at
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