[Pw_forum] G-vector in scf calculation

Gabriele Sclauzero gabriele.sclauzero at epfl.ch
Wed Nov 23 09:55:06 CET 2011

Dear Tram Bui,

Il giorno 23/nov/2011, alle ore 06.05, Tram Bui ha scritto:

> Dear QE Users,
>      I have an scf calculation on a zinc blend system with k-mesh 3x3x3 (automatic). And I obtained a G-vector value of around 120,000. Would anyone please give me some information on what the G-vector value represents?

This value tells you how many elements are included in the plane waves basis set that is used to expand the wavefunctions. Each G vector identifies a distinct plane wave function. The higher the number of G vectors, the more computationally expensive your calculation will be.

> and is there a relationship between the k-point and G-vector? 

Indirectly, yes. But the total number of G vectors should depend only very slightly on the chosen k-point mesh. On the other hand, it has a very strong dependence on the kinetic energy cutoff and on the cell size. I'm sure you'll be able to find more information by searching here: http://www.quantum-espresso.org/learn.php.



> Regards,
> Tram Bui
> M.S. Materials Science & Engineering
> trambui at u.boisestate.edu
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§ Gabriele Sclauzero, EPFL SB ITP CSEA
   PH H2 462, Station 3, CH-1015 Lausanne

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