Dear Paolo Thanks for your reply.
In fact I tried GGA(PBE) also. In this case the lattice parameter is better than GGA(pw91) (PBE = 10.313 a.u.) but is still less than that of LDA. If I generate new pseudopotentials for Ba, primarily which parameters would you suggest me to tune in order to improve the quality? regards munima > > On Jul 23, 2008, at 7:58 , Munima Bora Sahariah wrote: > >> For last couple of days I have been trying to find the equilibrium >> lattice >> constant of BaO with GGA (pw91) and has found that my calculated >> value >> underestimates the experimental one by 1.3% (GGA = 10.301 a.u., EXP = >> 10.431 a.u.). Surprizingly, while trying with LDA, I obtained a value >> which is closer to the experimental one as compared to GGA (LDA = >> 10.324 >> a.u.) [...] >> While doing a search on the web, I found one paper (Phys. Rev. B 71, >> 085203) where GGA and LDA results for lattice constant of BaO have >> been >> listed. In this paper calculations were done in CASTEP. Here the >> LDA value >> underestimates the experimental lattice constant while the GGA >> (pw91) value >> improves the situation and is closer to the experimental one. > > try different pseudopotentials if you can: this might be one of those > cases > in which the results are more sensitive than desired to the quality of > pseudopotentials (in particular of Ba). > > Paolo > --- > Paolo Giannozzi, Dept of Physics, University of Udine > via delle Scienze 208, 33100 Udine, Italy > Phone +39-0432-558216, fax +39-0432-558222 > > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > Dr. Munima B. Sahariah PI, DST Fast Track Project IASST, Guwahati Assam, INDIA ----------------------------------------------------------------------------------- This email was sent from IIT Guwahati Webmail. If you are not the intended recipient, please contact the sender by email and delete all copies; your cooperation in this regard is appreciated. http://www.iitg.ac.in
