On Sep 2, 2011, at 15:54 , Elie Moujaes wrote: > I have a simple question: does the total force acting > on a system depend on the number of k-points used?
not sure what you mean by "total force", but forces on atoms depend upon the number of k-points, for sure > That is in my scf calculation I am using a grid of 4x4x1 > for my system whereas the grid must be denser if phonon > calculations are taking place I am using 8x8x1. Do I get > different total force acting on the system and does it mean > I have to relax the crystal twice one for an scf calculation > and another for a phonon calculation? in principle a system should be relaxed for the same set of parameters (cutoff, k-points) that are used in the subsequent phonon calculation. The difference might be small enough to be negligible, but this is something that should be checked. P. --- Paolo Giannozzi, Dept of Chemistry&Physics&Environment, Univ. Udine, via delle Scienze 208, 33100 Udine, Italy Phone +39-0432-558216, fax +39-0432-558222
