Dear PWSCF users, I was wondering whether it is possible with PWSCF to optimize the unit cell while keeping the internal degrees of freedom (i.e. the reduced coordinates in the unit cell) fixed.
If this is not possible, I would like to ask you the following question: if I have, for example, an hexagonal system and I want to find how the c/a ratio evolves with pressure, I suppose I should calculate, for different volumes, the total energy as a function of c/a keeping the volume fixed. Then I would take the minimum point for each volume and with this build a E(V) curve, differentiate and calculate the P(V) curve. Is it correct to expect that at the c/a value at which, for each volume, the total energy is minimum, the stress tensor should be isotropic ? (i.e. the x,y,z components should be the same)? I expect that if I want to reproduce or compare with an experiment done at isotropic pressure I should perform my calculations at some values at which the stress tensor calculated from first-priciples is isotropic... is the above procedure correct? Thank you in advance for your response, Lilia
