[Pw_forum] Wrong effective charges in AFM insulator using "zue"

[Paolo Giannozzi]

On Jan 23, 2011, at 12:54 , xirainbow wrote:

> The three translational modes are about 70cm^-1 in paramagnetic  
> bulk material.
> How can I reduce them below 10cm^-1?

apply acoustic sum rule to the calculated dynamical matrices.
It is almost impossible to obtain from the linear response
calculation acoustic modes at q=0 with frequencies close
to zero.

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