I am trying to generate stress-dependent generalized stacking fault (GSF) energy curves for BCC metals. I have already generated these GSF curves for zero stress conditions using shrink-wrapped boundary condition in the slip plane normal direction (in my simulations the z direction). However, if I want to apply fix deform with a strain rate in the xz direction I get an error: “Cannot use fix deform tilt on a shrink-wrapped 2nd dim”. I have also tried fix npt at 1 Kelvin temperature with xz component of the stress tensor as Pstart = 0, Pend = 2000 and Pdamp = random number but end up with the same error as the fix deform attempt.
What I am aiming to accomplish is: for each given stress value ‘sigma’, the strain of the perfect crystal has to be adjusted so that sigma_xz = sigma is the only nonzero stress value. The strained crystal is then cut into two halves along the (112) plane and the two halves are displaced using displace_atoms relative to each other along the <111> direction (allowing vertical relaxation). My first attempt at this was with fix box/relax as this commands allows applying an external pressure or stress tensor to the simulation box during an energy minimization. However I need the z direction (plane normal to (112) plane) to be a free (shrink-wrapped) boundary for computing stacking fault energies. The difficulty with fix box/relax has led me to try the two other commands mentioned earlier.
Any help/suggestions are appreciated. Thanks!