[Pw_forum] matdyn.x: why are input/output k-points in the units of 2pi/a_0?

[Paolo Giannozzi]

Serge Nakhmanson wrote:

> PW manual for phonon calculations with &PHONON namelist
> calls for units of 2pi/a for xqq(i). As I understand, these
> are what you call "crystal coordinates" for k-points. 

no: crystal coordinates are in units of the crystal axis
of the reciprocal space

> for example, xqq = (0.5, 0.5, 0.5) for a tetragonal system
> would bring me into a corner of my BZ.

I don't think so: xqq = (0.5, 0.5, 0.5*(a/c)) would

> All my experience confirms that this procedure works well 
> and gives me phonons at the appropriate k-points.

Very strange

Paolo
-- 
Paolo Giannozzi, Democritos and University of Udine, Italy