Thanks for your responses. I figured out my errors. The problem has been resolved.
On Mon, Mar 28, 2022 at 3:50 PM Andrei Postnikov < andrei.postni...@univ-lorraine.fr> wrote: > Dear Francisco: > as a general statement, your expectation is justified. However, unexpected > things happen. > Having posted an (input) / output file would help to pinpoint a problem. > Without any additional information, I'd guess that your lattice vectors > are not exactly fcc, > or the atoms are not exactly at symmetric positions. (E.g., you think that > you scale > the atom coordinates with lattice parameter, but in fact you don't). > > Best regards > > Andrei Postnikov > > > ----- Francisco Garcia <garcia.ff....@gmail.com> a écrit : > > > Dear Users > > I performed a series of single point energy calculations on an FCC crystal > by varying the lattice constant. I'm trying to generate data points to > optimize the lattice constant > > I was expecting the force on each atom to zero by virtue of crystalline > symmetry (no internal degree of freedom). But to my surprise, the forces > are not zero. Increasing the Mesh cutoff from 300 Ry to higher values > didn't help either. How is it possible for the atomic forces in a crystal > to be non-zero? > > >
-- SIESTA is supported by the Spanish Research Agency (AEI) and by the European H2020 MaX Centre of Excellence (http://www.max-centre.eu/)
