I agree that is probably an effect of the supercell size. How big is the supercell that you are using?
Cheers, Sanda On Fri, Sep 18, 2009 at 8:47 AM, Duy Le <ttduyle at gmail.com> wrote: > if the defect concentration is too hight, when you do vc-relax the lattice > parameter will be re-optimized. In reality, the defect concentration is > about zero. > > On Fri, Sep 18, 2009 at 8:43 AM, xirainbow <nkxirainbow at gmail.com> wrote: > >> Dear: >> >> When you calculate without vc-relax, you deal with a point defect. >> When you use vc-relax, you change the crystal parameters. That is to say, >> you deal with a new kind of crystal, not a point defect. >> It is just my own point of view ?? >> >> >> >>> >>> Ali Kazempour >>> Physics department, Isfahan University of Technology >>> 84156 Isfahan, Iran. Tel-1: +98 311 391 3733 >>> Fax: +98 311 391 2376 Tel-2: +98 311 391 2375 >>> >>> --- On *Fri, 9/18/09, ali kazempour <kazempoor2000 at yahoo.com>* wrote: >>> >>> >>> From: ali kazempour <kazempoor2000 at yahoo.com> >>> Subject: defect formation energy >>> To: forum at democritos.it >>> Date: Friday, September 18, 2009, 5:31 AM >>> >>> >>> Hi >>> for study of point defect , i do relax calculation and obtain positive >>> defect formation energy while by vc-relax i gain negative. ? >>> what is the difference between positive and negative formation energy? >>> waht is the physical reasons? >>> thanks a lot >>> Ali Kazempour >>> Physics department, Isfahan University of Technology >>> 84156 Isfahan, Iran. Tel-1: +98 311 391 3733 >>> Fax: +98 311 391 2376 Tel-2: +98 311 391 2375 >>> >>> >> >> >> -- >> ____________________________________ >> Hui Wang >> School of physics, Nankai University, Tianjin, China >> >> _______________________________________________ >> Pw_forum mailing list >> Pw_forum at pwscf.org >> http://www.democritos.it/mailman/listinfo/pw_forum >> >> > > > -- > -------------------------------------------------- > Duy Le > PhD Student > Department of Physics > University of Central Florida. > > _______________________________________________ > 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/20090918/fb5aa81f/attachment.htm
