[Pw_forum] subroutine: star_q

[Paolo Giannozzi]

On Nov 22, 2006, at 12:28 , Katalin Gaal-Nagy wrote:

> I try to calculate for a given system the q points which are  
> equivalent
> to a given one. For this purpose I try to use the routine star_q given
> in the ph directory of the quantum espresso package [...]

the star_q routine is actually quite complicated. There are
several other places where this is done in the code; one
should be in PW/kpoint_grid.f90, another pwtools/kpoints.f

> The parameter noinv sets the inversion symmetry of the system

well, not exactly. "noinv" when .true. removes the effects of the
symmetry sending z into -z. This was an input variable used for
special purposes in cases (i.e. surfaces) but it is never read in
the recent versions. You can safely set it to .false.

> The parameter modenum is the number of modes to be done

no, it is the index of a specific phonon mode, used for
calculations of a single mode. Just set it to 0.

Paolo
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Paolo Giannozzi, Democritos and University of Udine, Italy