Thank you Prof. nicola, Lorenzo and Paolo. I got the point. Naol (Tamene)
On 6/24/09, pw_forum-request at pwscf.org <pw_forum-request at pwscf.org> wrote: > Send Pw_forum mailing list submissions to > pw_forum at pwscf.org > > To subscribe or unsubscribe via the World Wide Web, visit > http://www.democritos.it/mailman/listinfo/pw_forum > or, via email, send a message with subject or body 'help' to > pw_forum-request at pwscf.org > > You can reach the person managing the list at > pw_forum-owner at pwscf.org > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of Pw_forum digest..." > > > Today's Topics: > > 1. Re: smaller band gaps (Lorenzo Paulatto) > 2. Re: Separating Raman modes (Paolo Giannozzi) > 3. Re: smaller band gaps (Paolo Giannozzi) > 4. Re: Separating Raman modes (Zubaer Hossain) > 5. Re: Separating Raman modes (Paolo Giannozzi) > 6. hybrid functional and Wannier functions (lan haiping) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Tue, 23 Jun 2009 17:16:22 +0200 > From: "Lorenzo Paulatto" <paulatto at sissa.it> > Subject: Re: [Pw_forum] smaller band gaps > To: "PWSCF Forum" <pw_forum at pwscf.org> > Message-ID: <op.uvzgpku1a8x26q at paulax> > Content-Type: text/plain; charset=utf-8; format=flowed; delsp=yes > > In data 23 giugno 2009 alle ore 13:58:38, Naol Regassa > <greatnaol at gmail.com> ha scritto: >> My main concern is that DFT calculations reduce band gaps >> by 50%. > > DFT does not predict band gap at all, for many materials it is related to > the experimental one, but on assumption can be made a priori on its > precision. Anyway, you are probably doing the calculation using the > experimental lattice parameter, if you relax the system to the numerical > equilibrium lattice parameter, you will probably get a better gap. > >> Does this mean that I can add this error to get the correct >> band gap so that any body can understand it? How can one argue about >> this condition? > > No, the fact that DFT does not predict the band gap is a well known > problem of the theory, if you fix it with an empirical parameter it would > be not only unethical, but also quite suspicious. If you want to have > accurate band gap you have to use TDDFT or DFT+GW, which are both > implemented in quantum espresso (I don't know the details of them, nor > which is better for your specific purpose, you'll have to read a bit of > literature). > > best regards > > P.S. if you are starting a new discussion in the mailing list, please > write a new email, do not reply to a previous one > > > -- > Lorenzo Paulatto > SISSA & DEMOCRITOS (Trieste) > phone: +39 040 3787 511 > skype: paulatz > www: http://people.sissa.it/~paulatto/ > > *** save italian brains *** > http://saveitalianbrains.wordpress.com/ > > > ------------------------------ > > Message: 2 > Date: Tue, 23 Jun 2009 18:14:02 +0200 > From: Paolo Giannozzi <giannozz at democritos.it> > Subject: Re: [Pw_forum] Separating Raman modes > To: PWSCF Forum <pw_forum at pwscf.org> > Message-ID: <4A40FF4A.4070108 at democritos.it> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed > > Stefano Baroni wrote: > >> The method by Mauri and coworkers >> (whose implementation status in QE is unknown to me) > > it is implemented, but only for the "ordinary" phonon > code (i.e. not for the Gamma-specific one) and only for > norm-conserving pseudopotentials > > Paolo > -- > Paolo Giannozzi, Democritos and University of Udine, Italy > > > ------------------------------ > > Message: 3 > Date: Tue, 23 Jun 2009 18:18:24 +0200 > From: Paolo Giannozzi <giannozz at democritos.it> > Subject: Re: [Pw_forum] smaller band gaps > To: PWSCF Forum <pw_forum at pwscf.org> > Message-ID: <4A410050.9090100 at democritos.it> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed > > Lorenzo Paulatto wrote: > >> if you fix it with an empirical parameter it would be not only unethical > > Lorenzo, take it easy: there is nothing "ethically" wrong in trying > to adjust the gap, as long as it is clearly stated > > P. > -- > Paolo Giannozzi, Democritos and University of Udine, Italy > > > ------------------------------ > > Message: 4 > Date: Tue, 23 Jun 2009 11:28:30 -0500 > From: Zubaer Hossain <zubaexy at gmail.com> > Subject: Re: [Pw_forum] Separating Raman modes > To: PWSCF Forum <pw_forum at pwscf.org> > Message-ID: > <51ec861d0906230928p791f99a7yb86b747d6ad5facd at mail.gmail.com> > Content-Type: text/plain; charset="iso-8859-1" > > How about decomposing eigenstates into that for the individual atoms and > summing them for each species, since the phonon frequencies are computed > already, and the eigenmodes for each frequency are known. By analyzing these > quantities graphically for each species, optical frequencies of the main > three modes could be detected, I think. > > Zubaer > Department of Mechanical Science and Engineering > Univ. of Illinois at Urbana-Champaign, USA > > On Tue, Jun 23, 2009 at 11:14 AM, Paolo Giannozzi > <giannozz at democritos.it>wrote: > >> Stefano Baroni wrote: >> >> > The method by Mauri and coworkers >> > (whose implementation status in QE is unknown to me) >> >> it is implemented, but only for the "ordinary" phonon >> code (i.e. not for the Gamma-specific one) and only for >> norm-conserving pseudopotentials >> >> Paolo >> -- >> Paolo Giannozzi, Democritos and University of Udine, Italy >> _______________________________________________ >> Pw_forum mailing list >> Pw_forum at pwscf.org >> http://www.democritos.it/mailman/listinfo/pw_forum >> > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: > http://www.democritos.it/pipermail/pw_forum/attachments/20090623/b2f54fbb/attachment.html > > ------------------------------ > > Message: 5 > Date: Tue, 23 Jun 2009 18:35:42 +0200 > From: Paolo Giannozzi <giannozz at democritos.it> > Subject: Re: [Pw_forum] Separating Raman modes > To: PWSCF Forum <pw_forum at pwscf.org> > Message-ID: <4A41045E.5060708 at democritos.it> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed > > Zubaer Hossain wrote: > >> How about decomposing eigenstates into that for the individual atoms and >> summing them for each species, since the phonon frequencies are computed >> already, and the eigenmodes for each frequency are known. By analyzing >> these quantities graphically for each species, optical frequencies of >> the main three modes could be detected, I think. > > years ago we did something similar: > "Phonon Dispersions in Ga(x)Al(1-x)As Alloys", PRL 65, 84 (1990). > Alloy modes were projected over crystal modes. In that particular > case the "mass approximation" was giving an accurate and convenient > way to calculate the dynamical matrix in relatively large supercells > > Paolo > -- > Paolo Giannozzi, Democritos and University of Udine, Italy > > > ------------------------------ > > Message: 6 > Date: Wed, 24 Jun 2009 02:05:09 +0800 > From: lan haiping <lanhaiping at gmail.com> > Subject: [Pw_forum] hybrid functional and Wannier functions > To: PWSCF Forum <pw_forum at pwscf.org> > Message-ID: > <c92002fa0906231105l7b5918aeh44848111cbe1b20b at mail.gmail.com> > Content-Type: text/plain; charset="iso-8859-1" > > Dear All: > > I want to study electronic structures with hybrid functional. Is it > possible for us to using wannier90 package to analyse related bands at > present version ? Such as WFs and bands structure. > > > Regards, > > Hai-Ping > > > > -- > Hai-Ping Lan > Department of Electronics , > Peking University , Bejing, 100871 > lanhaiping at gmail.com, hplan at pku.edu.cn > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: > http://www.democritos.it/pipermail/pw_forum/attachments/20090624/ce0fac3b/attachment-0001.htm > > ------------------------------ > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > > > End of Pw_forum Digest, Vol 24, Issue 52 > **************************************** >
