Dear all? I am calculating phonon with QE-5.0.1. A 20x20x10 k-mesh is used in scf calculation. Phonon wave vectors are sampled on 10x10x5 mesh. But when I set degauss=0.03Ry in scf run, a imaginary frequency was found for the first branch with omega= -105.6 cm^-1 at wave vector (0.2, 0.346410162, 0.0). But if degauss=0.05Ry in scf run, this imaginary frequency disappear and become 132.1 cm^-1. Meanwhile, the frequencies of all other branches change slightly for these two degauss values. So my question is which results should I trust, degauss=0.03 Ry or 0.05Ry?
Btw: both lattice parameters and the inner coordinates of atoms are well relaxed for different degauss values. I am greatly indebted to you for your help. Thanks again! Best Miao Gao --------------------------------------- Ph.D. student of Department of Physics, Renmin University of China. --------------------------------------- -------------- next part -------------- An HTML attachment was scrubbed... URL: http://pwscf.org/pipermail/pw_forum/attachments/20130622/201a68f4/attachment.html
