Berry phase dipole + smearing

[Matt W]

Hi all,

I'm trying to do vibrational calculations using finite electronic temperature smearing for a periodic slab system.

At the moment Berry phase dipole moments aren't implemented, it seems, so no intensities. 

Could anyone give me some assistance to get them working (or point out that it is a fundamental problem). I'm thinking that it just needs rho%rho_ao(ispin)%matrix to be scaled by the occupation numbers appropriately in qs_moments, but maybe it is tougher?

Matt 

[hut...@chem.uzh.ch]

Hi Matt

this is a highly nontrivial problem. If you want to get the
basics, have a look at
I Souza, T. Wilkens, RM Martin, PRB 62 1666 (2000)

Short version is:
- the Berry phase formula only applies to insulators, not metals
- for an insulator with variable occupation, you need a model
for the all-electron wave function and then calculate
<Psi|exp(iGr)|Psi> where r=r1+r2+r3+... is. Maybe there is
a way using ensemble density functional theory.

best regards

Juerg

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

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To: cp...@googlegroups.com
From: Matt W
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Date: 02/19/2014 12:53PM
Subject: [CP2K:4958] Berry phase dipole + smearing

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[Matt W]

this is a highly nontrivial problem. If you want to get the
basics, have a look at
I Souza, T. Wilkens, RM Martin, PRB 62 1666 (2000)

Thanks, as I feared. 

I guess I can get dipole moments and hence intensities in the non-periodic direction if I run as a 2D system?

Matt

[hut...@chem.uzh.ch]

Hi Matt

yes, along the non-periodic direction you can just integrate
x*rho (use the non-periodic dipole).

For special systems, where the metal can be separated from the
rest you can also use Wannier functions (localize part of
spectrum with occupation 2).

Juerg

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

-----cp...@googlegroups.com wrote: -----
To: cp...@googlegroups.com
From: Matt W
Sent by: cp...@googlegroups.com

Date: 02/19/2014 02:31PM
Subject: Re: [CP2K:4960] Berry phase dipole + smearing