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
