Dear Paolo, thank you for your reply!
>> 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 I had the hope to get the equivalent q points in tha same ordering as in, e.q., the files with the dynamical matrices. That was the reason to take the routine star_q, since the ordering and, sometimes, also the sign of the componets is different for q sets calculated with pwtools/kpoints.f and PW/kpoint_grid.f90. Anyway. >> 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. Bene! I will do it. >> 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. I did it. Doing a small test it turned out that I get the same q points like in some dynmat-file, but with a different ordering. I am a little bit wondering, since the procedure is the same as in the ph.x program. But as long as it works for my (bct) system, I am fine. As soon as I have time I will do some checks also for systems with other lattices, and as soon as I have everything in a clean, documented way, I will give it to the pwscf (or better quantum espresso) community. Thank you for your help! Best wishes, Katalin
