Hi, I've read a number of forum posts about calculating elastic constants, but I was hoping someone could give me some advice. (I'm trying to calculate the elastic constants of bcc Iron).
From what I have read, there are two ways I could do this: 1) Relax the unit cell with vc-relax, deform the cell (by about 0.5-1%) and relax internally with relax. I'd then have the stress tensor of the deformed cell. 2) Deform the relaxed cell at regular strain intervals, then fit a polynomial to the strain-energy data. Am I right in saying I have those two options, or am I partly or completely wrong? If I tried the first option, it's been said to calculate the elastic constants from the strain-stress relationship. Would that mean solving the equation: Tij = Cijkl Ekl the ijkl are subscripts, T stress, E strain, C stiffness tensor I'm fairly new to the subject so I could be quite wrong in what I've said. Thanks Ben Palmer Student @ University of Birmingham UK