From claudio.attaccalite@gmail.com  Fri Feb  2 16:24:33 2007
From: claudio.attaccalite@gmail.com (Claudio Attaccalite)
Date: Fri, 2 Feb 2007 17:24:33 +0100
Subject: [Wannier] Nonorthogonal wannier function
Message-ID: <6b6a635f0702020824r45a4affcvfb1fc9720ef2103d@mail.gmail.com>

------=_Part_23338_18231374.1170433473790
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Content-Disposition: inline

Hi

a simple question:

1) it is possible to obtain nonorthogonal wannier functions (ok if want call
them very localized orbitals) with the wannier code?

2) if not, does someone know another code that does it? or you think it is
easy to modify the wannier code in such a way to relax the orthogonality
condition?

Thanks

Claudio


-- 
==========================================================
Claudio Attaccalite

Institute for Electronics, Microelectronics, and Nanotechnology
Dept. ISEN
B.P. 60069
59652 Villeneuve d'Ascq Cedex France
Skype: claudioattaccalite
web site: www.attaccalite.altervista.org
===========================================================

Freely download scientific books from: www.freescience.info

------=_Part_23338_18231374.1170433473790
Content-Type: text/html; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Content-Disposition: inline

Hi<br><br>a simple question:<br><br>1) it is possible to obtain nonorthogonal wannier functions (ok if want call them very localized orbitals) with the wannier code?<br clear="all"><br>2) if not, does someone know another code that does it? or you think it is easy to modify the wannier code in such a way to relax the orthogonality condition?
<br><br>Thanks<br><br>Claudio<br><br><br>-- <br>==========================================================<br>Claudio Attaccalite<br><br>Institute for Electronics, Microelectronics, and Nanotechnology<br>Dept. ISEN<br>B.P
. 60069<br>59652 Villeneuve d&#39;Ascq Cedex France<br>Skype: claudioattaccalite<br>web site: <a href="http://www.attaccalite.altervista.org">www.attaccalite.altervista.org</a><br>===========================================================
<br><br>Freely download scientific books from: <a href="http://www.freescience.info">www.freescience.info</a><br>

------=_Part_23338_18231374.1170433473790--

From marzari@MIT.EDU  Fri Feb  2 18:43:33 2007
From: marzari@MIT.EDU (Nicola Marzari)
Date: Fri, 02 Feb 2007 13:43:33 -0500
Subject: [Wannier] Nonorthogonal wannier function
In-Reply-To: <6b6a635f0702020824r45a4affcvfb1fc9720ef2103d@mail.gmail.com>
References: <6b6a635f0702020824r45a4affcvfb1fc9720ef2103d@mail.gmail.com>
Message-ID: <45C38655.3090900@mit.edu>


Dear Claudio,

the current Wannier90 code deals only with orthogonal wavefunctions.

Non-orthogonal WFs have been recently used in linear-scaling
quantum Monte Carlo approaches - both Andrew Williamson (Williamson
and Reboredo) and Dario Alfe' have developed some heuristic approaches
based on projections (a maximal localization strategy on non-orthogonal
WFs is somehow ill-conditioned: if you take a rare gas atom, the 
orthogonal MLWFs are 4 sp3 hybrids, but the non-orthogonal MLWFs would
probably be 4 identical s orbitals, each with an infinitesimal amount
of sp3 thrown in, to preserve linear independence).

Paolo Umari has coded the Williamson (or Alfe') algorithm as part of his
GW work, in a Gamma sampling implementation only - so I'm CC'ing him.

The plan on our side is to insert by the summer the orthogonal
Gamma-specific routines of localization and disentanglement into the
Wannier code (these have been written by Manu Sharma and Young-Su Lee).

Having a non-orthogonal option would also be great - and if you were 
interested or involved, it would also be great to coordinate.

				nicola



Claudio Attaccalite wrote:
> Hi
> 
> a simple question:
> 
> 1) it is possible to obtain nonorthogonal wannier functions (ok if want 
> call them very localized orbitals) with the wannier code?
> 
> 2) if not, does someone know another code that does it? or you think it 
> is easy to modify the wannier code in such a way to relax the 
> orthogonality condition?
> 
> Thanks
> 
> Claudio
> 
> 
> -- 
> ==========================================================
> Claudio Attaccalite
> 
> Institute for Electronics, Microelectronics, and Nanotechnology
> Dept. ISEN
> B.P . 60069
> 59652 Villeneuve d'Ascq Cedex France
> Skype: claudioattaccalite
> web site: www.attaccalite.altervista.org 
> <http://www.attaccalite.altervista.org>
> ===========================================================
> 
> Freely download scientific books from: www.freescience.info 
> <http://www.freescience.info>


-- 
---------------------------------------------------------------------
Prof Nicola Marzari   Department of Materials Science and Engineering
13-5066   MIT   77 Massachusetts Avenue   Cambridge MA 02139-4307 USA
tel 617.4522758 fax 2586534 marzari@mit.edu http://quasiamore.mit.edu

From dhv@physics.rutgers.edu  Sat Feb  3 16:37:50 2007
From: dhv@physics.rutgers.edu (David Vanderbilt)
Date: Sat, 3 Feb 2007 11:37:50 -0500 (EST)
Subject: [Wannier] Nonorthogonal wannier function
In-Reply-To: <45C38655.3090900@mit.edu>
References: <6b6a635f0702020824r45a4affcvfb1fc9720ef2103d@mail.gmail.com>
 <45C38655.3090900@mit.edu>
Message-ID: <Pine.SOC.4.64.0702031123350.17897@phonon.rutgers.edu>

Claudio, Nicola,

If you have in mind that the WFs are going to end up being roughly
atom-centered, so that each WF is identified with a given atom, then
I think it would not be very difficult to set up a framework in which
you ask for maxloc WFs that are orthonormal on-site but not between
sites.  If you have in mind a more general framework (e.g., where
some WFs may be bond-centered), then I'm not so sure such an approach
would make sense.

I'm not sure what the Williamson-Reboredo/Alfe schemes are, but I
think a projection scheme should work pretty well.  Note, however,
that simple projection is probably not good; one should do an extra
step to construct dual functions.  See the discussion in the top
paragraph, second column, p. 5343, of He and Vanderbilt,
http://prola.aps.org/abstract/PRL/v86/i23/p5341_1 .  Do the
Williamson-Reboredo/Alfe schemes include a step like this?

David

On Fri, 2 Feb 2007, Nicola Marzari wrote:

>
>
> Dear Claudio,
>
> the current Wannier90 code deals only with orthogonal wavefunctions.
>
> Non-orthogonal WFs have been recently used in linear-scaling
> quantum Monte Carlo approaches - both Andrew Williamson (Williamson
> and Reboredo) and Dario Alfe' have developed some heuristic approaches
> based on projections (a maximal localization strategy on non-orthogonal
> WFs is somehow ill-conditioned: if you take a rare gas atom, the orthogonal 
> MLWFs are 4 sp3 hybrids, but the non-orthogonal MLWFs would
> probably be 4 identical s orbitals, each with an infinitesimal amount
> of sp3 thrown in, to preserve linear independence).
>
> Paolo Umari has coded the Williamson (or Alfe') algorithm as part of his
> GW work, in a Gamma sampling implementation only - so I'm CC'ing him.
>
> The plan on our side is to insert by the summer the orthogonal
> Gamma-specific routines of localization and disentanglement into the
> Wannier code (these have been written by Manu Sharma and Young-Su Lee).
>
> Having a non-orthogonal option would also be great - and if you were 
> interested or involved, it would also be great to coordinate.
>
> 				nicola
>
>
>
> Claudio Attaccalite wrote:
>> Hi
>> 
>> a simple question:
>> 
>> 1) it is possible to obtain nonorthogonal wannier functions (ok if want 
>> call them very localized orbitals) with the wannier code?
>> 
>> 2) if not, does someone know another code that does it? or you think it is 
>> easy to modify the wannier code in such a way to relax the orthogonality 
>> condition?
>> 
>> Thanks
>> 
>> Claudio
>> 
>> 
>> -- 
>> ==========================================================
>> Claudio Attaccalite
>> 
>> Institute for Electronics, Microelectronics, and Nanotechnology
>> Dept. ISEN
>> B.P . 60069
>> 59652 Villeneuve d'Ascq Cedex France
>> Skype: claudioattaccalite
>> web site: www.attaccalite.altervista.org 
>> <http://www.attaccalite.altervista.org>
>> ===========================================================
>> 
>> Freely download scientific books from: www.freescience.info 
>> <http://www.freescience.info>
>
>
> -- 
> ---------------------------------------------------------------------
> Prof Nicola Marzari   Department of Materials Science and Engineering
> 13-5066   MIT   77 Massachusetts Avenue   Cambridge MA 02139-4307 USA
> tel 617.4522758 fax 2586534 marzari@mit.edu http://quasiamore.mit.edu
> _______________________________________________
> Wannier mailing list
> Wannier@quantum-espresso.org
> http://www.democritos.it/mailman/listinfo/wannier
>