[Pw_forum] negative phonon frequencies again :: graphene

[Paolo Giannozzi]

On Dec 20, 2012, at 12:25 , Martin Gmitra wrote:

> It seems that Martins-Troullier method for PP
> is more robust.

for phonon calculations in C, I am not sure I would
use USPP or PAW, unless there is a specific reason:
results with norm-conserving PP's are typically very
good and I don't think USPP or PAW are any faster
in this specific case.

The behaviour of your phonons at small q is definitely
strange. I have no idea why it occurs.

P.
---
Paolo Giannozzi, Dept of Chemistry&Physics&Environment,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222