[CP2K:4736] difference between wannier total dipole and berry total dipole

[hut... at pci.uzh.ch]

Yes, the reference (COAC) will change during a MD. Although
not 'jump' with the proton, as the oxygens have a much higher
weight.
Be careful when calculating charged systems! Now the dipole depends
on the choice of the reference point. If you change the reference point
during a MD also the dipole differences will change!

regards

Juerg

--------------------------------------------------------------
Juerg Hutter                         Phone : ++41 44 635 4491
Physical Chemistry Institute   FAX   : ++41 44 635 6838
University of Zurich               E-mail:  hut... at pci.uzh.ch
Winterthurerstrasse 190
CH-8057 Zurich, Switzerland
---------------------------------------------------------------

-----cp... at googlegroups.com wrote: -----
To: cp... at googlegroups.com
From: Wagner Homsi Brandeburgo 
Sent by: cp... at googlegroups.com
Date: 10/25/2013 03:46PM
Subject: Re: [CP2K:4736] difference between wannier total dipole and berry total dipole

Hi, I have another question on the same topic, 

in the case of using REFERENCE COAC (center of atomic charges) for calculating the total dipole of a protonated water system (bulk water + hydronium), 
if I understood it correctly the reference would be at the sum of the nuclear charges,
I was wondering if the reference would then jump together with the proton as it hops from one water molecule to the next. 

Cheers,
Wagner.


On Fri, Oct 25, 2013 at 2:56 PM,  <hut... at pci.uzh.ch> wrote:
 Hi
 
 Berry phase total dipoles are calculated from the determinant
 of the exp(-ikr) operator. For the Wannier total dipole first
 localized orbitals are calculated. Then the exp(-ikr) operator
 matrices are transformed into this new basis. Finally, the
 determinant is approximated by the product of the diagonal elements.
 This allows to sparate the dipole into molecular contributions.
 
 The two ways of calculation should give very similar total dipoles.
 Are you sure that you compare values with the same units?
 There is also the problem of 'branch', meaning that the calculated dipole
 is given +/- 2Pi/L.
 
 regards
 
 Juerg Hutter
 
 
 
 --------------------------------------------------------------
 Juerg Hutter                         Phone : ++41 44 635 4491
 Physical Chemistry Institute   FAX   : ++41 44 635 6838
 University of Zurich               E-mail:  hut... at pci.uzh.ch
 Winterthurerstrasse 190
 CH-8057 Zurich, Switzerland
 ---------------------------------------------------------------
 
 -----cp... at googlegroups.com wrote: -----
 To: cp... at googlegroups.com
 From: labicia
 Sent by: cp... at googlegroups.com
 Date: 10/24/2013 10:54AM
 Subject: [CP2K:4726] difference between wannier total dipole and berry total dipole
 

 Good morning!
 
 We are kind of new on this subject: may somebody tell us in a few words the difference between the wannier total dipole and berry total dipole.
 Or at least give us some reference to document ourselves?
 
 We are simulating a periodic bulk of methane.
 Are both methods suitable for this kind of system?
 
 The trend of the wannier total dipole and berry total dipole are almost the same, apart for a rescaling factor (total_wannier = 4.5 * total_berry + K), with K a constant.
 
 Thank you very much,
 and be patient if the question is a bit trivial,
 Marco and Andrea
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