On Apr 4, 2011, at 8:43 , Stefano Baroni wrote: > shouldn't it rather be exp(+i k*r)? (for the few who would care ...) yes, sure 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