From claudio.attaccalite at gmail.com Fri Feb 2 17:24:33 2007 From: claudio.attaccalite at gmail.com (Claudio Attaccalite) Date: Fri, 2 Feb 2007 17:24:33 +0100 Subject: [Wannier] Nonorthogonal wannier function Message-ID: <6b6a635f0702020824r45a4affcvfb1fc9720ef2103d@mail.gmail.com> 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 -------------- next part -------------- An HTML attachment was scrubbed... URL: From marzari at MIT.EDU Fri Feb 2 19:43:33 2007 From: marzari at 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 > > =========================================================== > > Freely download scientific books from: 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 at mit.edu http://quasiamore.mit.edu From dhv at physics.rutgers.edu Sat Feb 3 17:37:50 2007 From: dhv at 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: 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 >> >> =========================================================== >> >> Freely download scientific books from: 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 at mit.edu http://quasiamore.mit.edu > _______________________________________________ > Wannier mailing list > Wannier at quantum-espresso.org > http://www.democritos.it/mailman/listinfo/wannier >