On Mon, 2012-11-12 at 08:13 +0000, Sakhrawi Taoufek wrote: > i want to fix the volume and each time calculate the total energy to optimize the lattice parameter, > there is any idea how to proceed. $ grep -i volume PW/Doc/INPUT_PW.def shape = all axis and angles, keeping the volume fixed -- Paolo Giannozzi, IOM-Democritos and University of Udine, Italy