[Pw_forum] *.fc file in PW_SCF help.

[xirainbow]

Dear Stefano de Gironcoli:



> >because they are obtained by a FFT on a discrete regular grid of q
> vectors.
> >look (google or numerical recipes) for spectral analysis by Fourier
> >transform.
> >An understanding of aliasing errors in FFT may also be useful.
> >There is a relationship between the density of q-point grid and the
> >extent to which interatomic force constants are accurately described in
> >real space... or rather  the opposite ...  between the extent of IFC in
> >real space and the density of q-point grid needed to accurately describe
> >them.

Thanks again for your patient explanation.


>
> >think of one spring connecting 2 balls.. E=1/2 K (x1-x2)^2
> >what is the force between one atom and itself ?

Sorry, I can not grasp what want tell me:(
Could you explain it more directly?

____________________________________
Hui Wang
School of physics, Nankai University, Tianjin, China
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