Dear Mostafa Thank you for your detailed answer. you wrote 'In fact, although literature clearly shows that DFT+U predicts qualitatively problematic phonon dispersion for soft-mode materials such as TiO2' could you please cite some references? i tried to find some, but i could not find any source to validate the claim. thanks Adnan
On Thu, Aug 13, 2015 at 3:56 AM, Mostafa Youssef <myous...@mit.edu> wrote: > Dear Muhammad , > > This is really tricky. Using DFT+U for 0K energies followed by DFT for > phonons is a bit inconsistent. I would rather be consistent and understand > the limitations of the theory rather than trying to mix inconsistent parts > together. > > You could ignore the vibrational contribution as suggested by Jia Chen , > although I think at high temperature this contribution might be > significant. Alternatively you could resort to the extremely expensive > hybrid functionals to do both 0K energies and phonons (within frozen > phonon approximation). Another sound alternative is just to use DFT+U for > 0K energies and phonons with the clear understanding that therer might be > some error associated with the phonons part. In fact, although literature > clearly shows that DFT+U predicts qualitatively problematic phonon > dispersion for soft-mode materials such as TiO2 , there has not been a > systematic investigation of the performance of DFT+U in predicting > vibrational free energy *differences* between a perfect crystal (TiO2) and > a defective one (TiO2-x) for this class of materials. I would be very > interested if somebody can point out to a paper that addressed this. > > > Mostafa Youssef > MIT > > <http://www.mail-archive.com/search?l=pw_forum@pwscf.org&q=from:%22Muhammad+Adnan%22> > > _______________________________________________ > Pw_forum mailing list > Pw_forum@pwscf.org > http://pwscf.org/mailman/listinfo/pw_forum > -- Best Regards Muhammad Adnan Saqlain
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