[CP2K-user] [CP2K:15388] Keywords in KPOINTS section

hut... at chem.uzh.ch hut... at chem.uzh.ch
Mon May 17 12:43:19 UTC 2021


some additional information on the kpoints keywords:

FULL_GRID T/F : If false uses time reversal to reduce number of k-points (default)
Symmetry T/F  : Reduces number of kpoints according to symmetry operations (this is
                currently not availbale in CP2k)
Wavefunction Real/Complex : orbitals in kpoint calculations are by default complex.
                            For some specific choices of kpoints (gamma point, zone boarders)
                            wfn can be chosen to be real. 


Juerg Hutter
Juerg Hutter                         Phone : ++41 44 635 4491
Institut für Chemie C                FAX   : ++41 44 635 6838
Universität Zürich                   E-mail: hut... at chem.uzh.ch
Winterthurerstrasse 190
CH-8057 Zürich, Switzerland

-----cp... at googlegroups.com wrote: -----
To: cp... at googlegroups.com
From: "Lucas Bandeira" 
Sent by: cp... at googlegroups.com
Date: 05/16/2021 07:09PM
Subject: [CP2K:15388] Keywords in KPOINTS section

Dear cp2k community,

I am trying to understand some of the keywords in the KPOINTS section. They are the WAVEFUNCTIONS, FULL_GRID, and SYMMETRY keywords. 

If I set FULL_GRID TRUE, will integrals also be evaluated outside the Irreducible Brillouin Zone? Or this keyword has nothing to do with it. When should I set it to TRUE or FALSE?

About the WAVEFUNCTION keyword, when should I set it to REAL or to COMPLEX? In the cp2k exercise to compute the band structure of graphene, it was set to REAL, but I had some problems using it for metallic systems, so I swapped it to COMPLEX.

About the SYMMETRY keyword, I am optimizing the geometry of a cubic metallic bulk. So it is OK to set it to TRUE. But, when working with slabs, I should set it to FALSE, because the vacuum layer removes the symmetry of the system. Is that right? Could somebody give me other examples of when I should set it to TRUE or FALSE?

Yours sincerely, 

Lucas Bandeira

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