Dear Sir, (1) Here i am running Black phosphorous, which is layered compound crystallizes in orthorhombic structure and reported that having huge van der waals forces. Generally systems having van der waals forces shows huge 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 up to 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. (2) What is the difference in structural optimization between normal process( optimizain c/a, b/a and a with energy) and "vc-relax"? Thanks in advance. 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/20110921/1166c7a0/attachment.htm
