ON THE VOLUME DEPENDENCE OF COMPUTED GRAIN BOUNDARY ENERGY.

To avoid inaccurate boundary energies, completely free and unconstrained borders should ideally be applied. The degree of freedom along the direction in which the boundary structure is not periodic is important. Alternatively, if fixed borders are used, models large enough so that the compressive strains have a negligible effect on the boundary energy and structure should be used. In small models and changing the volume, care should be taken in calculating the total energy correctly. When using non-equilibrium potentials this procedure is invalid since the total energy should be minimized, not just the pair contribution. In this case the free electron contribution Pdv has to be added to the expanded structure energy.