Dear Premlata, It's normal for LDA to underestimate the lattice but in your case the error is about 4%. I would start to get nervous. One usually aims at 1 or at most 2 percent. I suggest you try other pseudopotentials and/or try to make sure that you are getting good fits for your Ecut, Nk, smearing (if necessary) parameters. By a "good curve" I mean one which is not too bumpy.
Best, Hande On Fri, 8 Aug 2008, premlata pandit wrote: > hello > the experimental lattice constant of Li2S is 10.7867 a.u. > and my calculated equlibrium lattice constant is 10.375 a.u. by using LDA > pseudopotential in pwscf calculation. > can i use this lattice canstant to calculating elastic constants? > > -- Hande Toffoli Department of Physics Office 439 Middle East Technical University Ankara 06531, Turkey Tel : +90 312 210 3264 http://www.physics.metu.edu.tr/~hande
