[Pw_forum] easy question

[kanta_chan25 at yahoo.co.jp]

Dear all,

It is begun these days to use QE and DFPT is studied. 

There is an easy question. 

Electron density(n(r)) is made from the plane wave set in this code? 

A plane wave cannot be dependent on nuclear coordinates.(exp(ikr))

In DFPT, the differentiation in the nuclear coordinates of electron density is required. 

I will think that the differentiation in the nuclear coordinates of electron density will disappear. 
If surely a nucleus changes, density is also likely to change. 
However, a base is a plane wave. 
It is not dependent on a nuclear position.

sum of plane wave set (sigma {exp(ikr)}) →　density n(r) → dn(r)/dR is vanish ... ???

Where do I mistake? 

please help me.


Best,
Tomson
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20130705/e67c0db9/attachment.html>