Dear Shi Kong, We have very few data to answer properly to your question. What are the available experimental data and more specifically: 1/ Do you have the atomic structure (cell param. and atomic positions) for different pressures or only cell parameters variation with pressure? 2/ In the "normal" structure how many equivalent sites do you have for the f-element? 1 or more?
If you have one equivalent position for the f-element in the "normal" structure, then in the supercell you have many inequivalent sites for the f-element. In other words, during the calculation of the small cell you can easily converged to metal state because all f-atoms are equivalently occupied. In contrast, in the supercell you allow to have different electronic configurations for the f-atoms in inequivalent sites. In such situation, you should be very careful during the SCF convergency, because you could have charge oscillations due to the alternative occupation of the inequivalent f-atoms. In addition, you should need to help the system to converge towards the "global" minimum electronic configuration using such an approach: - change the smearing method (efmod in case.in2), i.e. use GAUSS for instance with large eval value at the beginning to 0.05 - reduce progressively eval But it should also be due to an incorrect model for the high pressure structure: - because you do not have enough or accurate experimental data - because the supercell you have generated exhibits an ordering which lead to the opening of a band gap. Regards Xavier kongshi a ?crit: > Dear WIEN2k users: > Recently I'm calculatingthe f-electron material under pressure with > LDA+U.There are different results between with normal structure file > and with supercell structure file. The result of normal structure file > with symmetry under pressure is metal. But the supercell structure > under pressure result is insulator.The result of spuercell structure > file in atmospheric pressure is metal. In my opinion the pressure > drive the material to the metal state. > Can anybody tell me what the problem is? Thank you in advance. > shi kong > > > __________ Information from ESET Smart Security, version of virus > signature database 4821 (20100130) __________ > > The message was checked by ESET Smart Security. > > http://www.eset.com > ------------------------------------------------------------------------ > > _______________________________________________ > Wien mailing list > Wien at zeus.theochem.tuwien.ac.at > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://zeus.theochem.tuwien.ac.at/pipermail/wien/attachments/20100131/abc457e8/attachment.htm>