Relaxation for no-period boundary condition box

Dear all,

In the procedure of grain boundary energy calculation, a box with specified boundary conditions must be defined. After a bicrystal with predetermined misorientation has been constructed, relaxation must be applied to get the equilibrium state of such bicrystal. Then grain boundary energy could be calculated according to the potential difference between this equilibrium bicrystal and corresponding perfect lattice bulk and the grain boundary area.

My question is, due to 'fix box/relax command' can be work only in period boundary condition, how to implement such a relaxation for a box with free surface boundary condition.

Thanks a lot.

There is no point to relaxing a box when you have no periodicity.