Dear users,
I am trying to calculate NMR chemical shifts by GIPAW for a crystal (with atoms Al, P, O). The pps I used with GIPAW are "pbe-tm-gipaw-dc" sets. I did get reasonable results. For a second step I tried to optimize the structure. I noticed if I still used the gipaw pps, the optimization process is completely wrong. In vc-relax calculations the cell volume keeps shrinking to 67% of original volume (which is from experimental structure). While I changed the pps to "pbe-n-kjpaw" set, vc-relax gave reasonable results. I would be very thankful if someone can explain a little bit for me what kind of pps are not suitable for optimization so in future I can avoid similar mistake? Any helps will be greatly appreciated. Best regards, James Mao Postdoc associate Department of Chemistry, University of Pittsburgh -------------- next part -------------- An HTML attachment was scrubbed... URL: http://pwscf.org/pipermail/pw_forum/attachments/20140128/0e3317bb/attachment.html