Dear Jiayu in order to fully account the effects of the +U correction on pressure one should include a contribution from dU/dV too. you may find this reference useful:
Phys. Rev. B 12, 125124 (2009) regards, Matteo Jiayu Dai wrote: > Dear Matteo, > > Thanks for your comments. I am using the BOMD (pwscf). In my case, at high > density, i would expect the U should be different with the change of ionic > structures. In particular, i am concerning about the pressure. I found a > strange thing: the pressure with LDA+U is lower than the pressure without U > adding. As my experience, th pressure should be larger when we added the U > parameter, is it right? > > Besides, all the cases using LDA+U is about the transition metals, which has > the d or f electrons. How about the s or p electrons? > > Thanks. > > Jiayu > > > > > Dear Jiayu, > > are you talking about Car-Parrinello MD or Born-Oppenheimer MD (run with > pwscf)? > In any case lda+U MD is implemented in the sense that the code computes > the forces and the stress > as derivatives of the lda+U energy functional. However it is not able > to account for the variation > of U with atomic position or with the cell. So it is a dynamics at fixed U. > To account for this variation one would need to evaluate dU/dR or > dU/d\epsilon (R and \epsilon being atomic > positions and strains). Some work in this direction has been recently > done (not sure it's > published yet) by Kulik and Marzari. > If the structure you are interested in doesn't change dramatically > during the MD run I would expect > that keeping the same U is not too bad. but this is just my guess. > > regards, > > Matteo > > > Jiayu Dai wrote: > >> Dear developers, >> >> I have some doubts about the molecular dynamics calculations using LDA+U. >> First, is LDA+U performed in MD calculations? Because i did not find the >> Hubbard energy in the output file of MD. Second, i think the value of U be >> dependent on the temperature and density, also on the ionic structures. >> Therefore, since ionic positions are different in each time step, is U >> different at each time step? If so, the performance of LDA+U should be very >> difficult in MD. >> >> I did not know if what i said is right. Hope experts comment on this problem. >> >> Thanks a lot. >> >> Jiayu >> ------------------------------------------- >> Jiayu Dai >> Department of Physics >> National University of Defense Technology, >> Changsha, 410073, P R China >> ----------------------------------------- >> _______________________________________________ >> Pw_forum mailing list >> Pw_forum at pwscf.org >> http://www.democritos.it/mailman/listinfo/pw_forum >> >> > > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > -- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Matteo Cococcioni Department of Chemical Engineering and Materials Science, University of Minnesota 421 Washington Av. SE Minneapolis, MN 55455 Tel. +1 612 624 9056 Fax +1 612 626 7246 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
