[Pw_forum] accustic sum rule on soft phonon mode

W. YU yuwen_66 at yahoo.com
Tue Sep 20 09:44:50 CEST 2005

Dear PW users,

I met a problelm during phonon calculation.  When I
use accoustic sum rule (ASR) with dynmat.x on a system
with soft mode, the positive frequencies were only
slightly affected, but the soft mode frequency changed
a lot. In this case, can I still use ASR and trust the
soft mode frequency given by dynmat.x? 

Bye the way, I know it is possible to apply accoustic
sum rule to effective charge manually. If I only do
phonon calculation at a single q point, say X point
for silicon, can Is there a way (manually if
possible)to ensure accoustic sum rule as done by
dynmat.x with phonon dispersion curves?

Any comments would be much appreciated!


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