Consistent methodology for calculating surface and interface energies

A consistent approach to the calculation of the surface energy: valid for all crystal systems is presented. Voronoi polyhedra are introduced and used in conjunction with the energy-density formalism of Chetty and Martin [Phys. Rev. B 45, 6074 (1992); 45, 6089 (1992)] to provide a methodology for the determination of surface energies. The surface energies of the unrelaxed, unreconstructed GaAs (001) and (111) surfaces are calculated as a test. As an example of the application of the formalism to a low symmetry system, the energies of selected (0001) surfaces of the wide-gap semiconductors GaN and SiC are determined.