The mechanical interaction of point defects in a face-centred cubic lattice

The interaction energy between a pair of identical point defects is calculated for a discrete face-centred cubic lattice which is held together by first-neighhour generalized forces. By a suitable choice of force constants a lattice which is elastically isotropic in the long wavelength limit is obtained. For this lattice an analytic expression for the interaction energy is when the defect spacing, R, is large. The interaction energy has the Hardy-Bullough R −5 dependence but witha different angular variation to that previously given. Numerical results are presentedfor the anisotropic near-neighbour ctwe.