I'm sorry for attaching Luiz's mail by mistake. I rewrite my mail. Really
sorry. Hi, QE users.Recently I plan to perform free energy calculations of CO
absorption using ph.x, matdyn.x, q2r.x and fqha.x. However, I meet mainly 2
problems.1. When I do phonon calculation of isolated CO molecule with q points
sampling automatically 2x2x2, I find large negative frequency emerges in DOS.
Could anyone tell me why ph.x yields negative frequency? Moreover if I want to
eliminate the negative frequency, should I decrease the tr2_ph value?2. When I
do phonon calculation of the CO absorbed slab, to simplify the calculation, I
set start_irr and last_irr parameters including three translational degrees of
freedom of C and O atom. However, after each q point iteration, ph.x outputs
one line like:Not Davison diagonalization, representation 0 is not done.As a
result, no frequency information is yielded, although ph.x job terminates
normally. However, it is hard to understand representation 0, because
irreducible representation in ph.x is marked from 1, not 0. I don't know how I
can solve this problem.Any suggestions will be appreciated. Best regards.Yike
HuangPhD candidate.Dalian Institute of chemistry and physics, CAS, China.
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