I want to calculate the most accurate bulk energy and the a-priori information I have are the atomic positions.
On Fri, Mar 1, 2013 at 1:59 PM, Laurence Marks <L-marks at northwestern.edu>wrote: > My two cents. Both LDA+U and GGA+U are wrong. That said, for f-/d- systems > they are often better than LDA/GGA for some properties. The question you > should ask yourself is what property are you trying to measure/predict, and > what a-priori information (reference state) do you have that can be used? > > For instance, if I want to calculate a surface energy then I would tune > the U to give the most accurate bulk energy treating this as my a-priori > information; similarly if I wanted to calculate the elastic behavior of a > defect I would tune to the bulk elastic constants. In my opinion this is > the only justifiable approach. > > > On Fri, Mar 1, 2013 at 12:47 PM, Zsolt Rak <zsolt.rak at gmail.com> wrote: > >> Dear wien2k users, >> >> I am calculating the properties of several f-electron compounds. I would >> like to ask the users' opinion about the volume optimization in an f- or >> d-electron system: which way is better (or physically justified), with >> LDA/GGA or with LDA+U/GGA+U? In my opinion, the LDA+U/GGA+U techniques were >> developed to correct band energies of localized states, so there is no >> fundamental physical reason to use LDA+U/GGA+U methods for volume >> optimization. However, we observe a change in the lattice parameters when >> we go from LDA/GGA to LDA+U/GGA+U. Also, from a brief search of the >> literature we found that, in many cases, people tune the Hubbard-U >> parameter to reproduce the experimental lattice constants. >> I would appreciate further thoughts and insights into this issue. >> >> Thank you, >> Zs >> > > > > -- > Professor Laurence Marks > Department of Materials Science and Engineering > Northwestern University > www.numis.northwestern.edu 1-847-491-3996 > "Research is to see what everybody else has seen, and to think what nobody > else has thought" > Albert Szent-Gyorgi > > _______________________________________________ > Wien mailing list > Wien at zeus.theochem.tuwien.ac.at > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://zeus.theochem.tuwien.ac.at/pipermail/wien/attachments/20130301/5416e3c3/attachment.htm>