Dear Sir, Thank you for your reply. I am sorry for not sending complete details. Here i am running Black phosphorous, which is layered compound and reported that havng huge van der waals forces. Genarally systems having van der waals forces shows volume change( either 10-12% underestimate in LDA or 5-6% overestimate in GGA) with experimental volume in DFT calculations. In my case,CASTEP and VASP i got similar variation in volume. But in PwSCF, i got 2% volume change with experimental volume. Here i used 50Ry cutoff and 10X10X10 K-mesh is used for my calculations. For energy minimum i used upto 10e-8 .Where as in "vc-relax" calculations i got 10% volume change with experimental volume.
please give your suggestions for my problem. If it is need i will send my b/a, c/a and a calculation input and output files to your mail. with regards S.Appalakondaiah Research scholar University of Hyderabad Hyderabad -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20110918/f0641585/attachment.htm
