where E I GB is the interface energy of the GB, E GB is the energy of the GB supercell, n Si is the number of silicon atoms in the GB, E BulkSi is the per atom energy of bulk diamond cubic silicon, n Al is the number of aluminum atoms in the GB, E BulkAl is the per atom energy of bulk fcc aluminum and A is the interface area of the GB. The factor 2 is incorporated to indicate the presence of two GBs in the unit cell.