On Apr 10, 2010, at 15:47 , mohnish pandey wrote: > As you can see there is perssure is different in final vc-relax and > scf calculation.
this has been explained no less than 36000 times: the number of plane waves depends upon the starting cell volume of a vc-relax calculation, so it may differ from the number of plane waves used in a scf calculation with the same final geometry. In your case the difference in presure is so ridicolously small that it doesn't deserve to be called a difference. > After that I am doing phonon calculation and I am getting some > frequencies to be negative. and this has been explained a litle bit more than 72000 times: http://www.quantum-espresso.org/user_guide/ node79.html#SECTION00097030000000000000 P. --- Paolo Giannozzi, Dept of Physics, University of Udine via delle Scienze 208, 33100 Udine, Italy Phone +39-0432-558216, fax +39-0432-558222
