Dear Gabriele I compeletly agree with you. I work on graphene and it seems that it is not necessary to use 2 2 2/4 4 4 grid. I just used them to see that as Eyvaz suggested my error would be diappeared or not. Now I don't have any problem with espresso-4.0.5 & thanks a lot because of your help. I have another question when I use c.blyp-mt.UPF pseudopotential and then calculate frequency in gamma point, my optical frequency is about 3400cm-1 but when I use 2 2 1 grid I gain 1528cm-1. I couldn't understand the reason of it Best Regards Mehrnaz Iran University Of science & Technology
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