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

[xirainbow]

 Dear Professor Paolo:
Thank you for your valuable instruction:)

Why is it almost impossilbe to obtain zero for tranlational modes from the
linear response calculation?
Does finite displacement method (frozen phonon) can get zero?
Does it relate with spatial discretization?
I am interested in it:)



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

-- 
____________________________________
Hui Wang
School of physics, Fudan University, Shanghai, China
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