On Apr 7, 2011, at 9:40 , xirainbow wrote: > Based on the definition of Born effective charge, it is a "real > symmetric matrix“. real, but not symmetric, in general 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