Dear Paolo, thanks for your answer. Indeed, I am using Yambo which requires that flag.
The point is that Andrea Marini and I are working on a Wannier90 interface for Yambo. While for the generation of the automatic grids the increased number of k points is perfectly ok, the problem arises when we have to generate the full k grid that is needed by Wannier90. In this case, in fact, if for instance I specify the 64 k points for a 4x4x4 grid in the nscf calculation, and I leave the force_symmorphic flag set to true, QE will calculate the band energies on 136 k points instead. Of course for this nscf calculation I can simply remove the force_symmorphic flag, I was just wondering if it could make more sense not to increase the number of k points if they are given as an explicit list (but maybe there are cases for which instead this is the intended behavior). Giovanni On 06/20/2012 06:27 PM, Paolo Giannozzi wrote: > On Wed, 2012-06-20 at 17:46 +0200, Giovanni Pizzi wrote: >> > I was using the force_symmorphic flag of pw.x. > you shouldn't, unless you have a good reason to use it > >> > I noticed that even when I provide an explicit list of k points >> > (e.g. with >> > K_POINTS crystal >> > or even >> > K_POINTS crystal_b >> > for a band structure) pw.x increases the number of k points. > "force_symmorphic" just removes the symmetry operations having > an associated fractional translation from the list of allowed > symmetries. Any change in the number of k-points, if any, is > a consequence of the reduced symmetry of the system. > >> > Is this the intended behavior, or should the list of K points be >> > modified only for K_POINTS automatic? > hard to say what the "intended" behavior is: there isn't any. > That option was added (by me) in order to allow PWscf to produce > data for other codes (don;t remember which ones) that do not > implement nonsymmorphic symmetry groups. > > P. > -- Paolo Giannozzi, IOM-Democritos and University of Udine, Italy -- Giovanni Pizzi Post-doctoral Research Scientist EPFL STI IMX THEOS MXC 319 (B?timent MXC) Station 12 CH-1015 Lausanne (Switzerland) Phone: +41 21 69 31159
