[CP2K:6432] Problems with GAPW + external potential

[hut... at chem.uzh.ch]

Hi

yes, this is a bug. The external potential is applied to the
charge on the plane wave grid. In GAPW only the soft part
of the charge is on the grid and one would have to also compute
the contributions from the local atomic charges.

regards

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: Juha Ritala 
Sent by: cp... at googlegroups.com
Date: 04/29/2015 09:52AM
Subject: [CP2K:6432] Problems with GAPW + external potential

I have had some problems when I tried to use GAPW method combined with an external potential. To demonstrate what seems to be the source of the problems, I made this simple test case with a water molecule in a constant external potential. Physically, the constant background potential should not affect the total energy of the water molecule since the molecule is charge neutral. The energy does change as a function of the constant potential when the GAPW method is used, however. You can see this in the attached energy vs. background potential plot. GPW method gives expected behaviour, the total energy stays perfectly constant when the potential is varied.

It seems as if some part of the charge in the system is unaffected by the external potential in GAPW and thus the total charge is effectively non-zero. Is this a bug or is there some part of the implementation missing?




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[attachment "E_vs_V_GAPW_and_GPW.pdf" removed by Jürg Hutter/at/UZH]
[attachment "H2O_constant_extpot_GPW.inp" removed by Jürg Hutter/at/UZH]
[attachment "H2O_constant_extpot_GPW.out" removed by Jürg Hutter/at/UZH]
[attachment "H2O_constant_extpot_GAPW.inp" removed by Jürg Hutter/at/UZH]
[attachment "H2O_constant_extpot_GAPW.out" removed by Jürg Hutter/at/UZH]