There is nothing wrong so long as this is only a few percent although this is a bit unusual. Normally PBE gives lattice constants too large, LDA too small with PBEsol & WC closer to experiment. I myself do not consider agreement between expt & calculated lattice constants (within a few percent) to be a very useful test of functionals despite what is in the literature.
______________________________ Laurence Marks Dept Mat Sci & Eng Northwestern University www.numis.northwestern.edu 847 491 3996 On Jan 30, 2014 8:13 AM, "kalsoom Khan" <kkkhan.qu...@yahoo.com> wrote: > Dear all > I have problem in optimization, i want to optimize the the lattice > constant.. but i have contrast in the reults. I did the optimization for > two cubic compounds, in which for one compound the lattice constant > increased from the experimental values. While for the other compound the > lattice constant were decreased. > so please help me that which one is wrong. Either the optimized lattice > constant increased or decreased. > with regards > kalsoom >
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