[Pw_forum] negative phonon frequencies again :: graphene

[Martin Gmitra]

Dear Lorenzo,

The QE code version is 5.0.1. I think that improvement can be achieved
when denser k-mesh for self-consistent
calculation is considered. What still remains puzzling for me is why
other PPs (rrkjus, uspp ak) do not behave
(see attached figure, k-mesh is 40x40) like C.pbe-mt_fhi.UPF? It seems
that Martins-Troullier method for PP
is more robust. Could anyone comment on it please?

Best regards,
Martin Gmitra

Universität Regensburg
Institut I - Theoretische Physik
Universitätsstraße 31
D-93040 Regensburg
Deutschland/Germany
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