Hi Francesca,
> / > &system > ibrav = 8, celldm(1) = 29.02243, celldm(2) =1.0, celldm(3)= 0.89771, > nat=56, ntyp=2, ecutwfc=18.0, > / >... > ATOMIC_SPECIES > Si 28.086 Si.pw91-n-van.UPF > H 1 H.pw91-van_ak.UPF since you are using ultrasoft pseudopotentials (USPP), besides ecutwfc, you should also specify ecutrho... as a default ecutrho = 4 * ecutwfc, and this is what it is analytically obtained for norm-conserving pseudopotentials... in the case of USPPs, typical values for ecutrho range from 8 to 12 times ecutwfc (as a rule of thumb to be tested) of course, this can explain convergence problems look also in the forum archive where this topic has been already discussed... cheers andrea -- Andrea Ferretti National Research Center S3, CNR-INFM ( http://s3.infm.it ) Dip. Fisica, Univ. di Modena e Reggio E. (Italy) Tel: +39 059 2055301; Fax: +39 059 374794; Skype: andrea_ferretti URL: http://www.nanoscience.unimo.it Please, if possible, don't send me MS Word or PowerPoint attachments Why? See: http://www.gnu.org/philosophy/no-word-attachments.html
