Eyvaz Isaev wrote: > [...] first I did phonon calculations for a base centered > orthorhombic cell (ibrav=9) using 4x2x2 mesh (10 q-points) > and got an error message from q2r.x "q not allowed" [...] > Then I tried to generate q-points using kpoints.x which stated > that 4x2x2 mesh "has not the correct symmetry" and gave only > 6 q-points. OK, I used 4x3x3 to generate q-points and got 10 > q-points without any message from kpoints.x. But when I started > phonons with 4x3x3 q-mesh, the ph.x program generated 14 q-points. > > Can someone explain such kind discrepancy between two programs > generating q-points?
I cannot (yet) explain why the two programs behave in a wrong but different way, but I have half an idea of what triggers this bug. With this Bravais lattice (which, by the way, kpoints.f90 incorrectly reports as "orthor 1-(fco)"), axis 1 and 2 have the same length, different from the length of axis 3. So you should use a 2x2x4 mesh, or a 3x3x4, not the ones you used. I don't see why this confuses the logic of the symmetry check, though, since there are no symmetry operations sending axis 1 into 2. Paolo -- Paolo Giannozzi, Democritos and University of Udine, Italy
