A self-consistent pseudopotential calculation of the diamond-metal interface is used to examine interface states and empirical correlation for the dependence of the Schottkybarrier height and interface index, S, on ionicity. The properties of diamond are crucial because of its large gap and zero ionicity. Predictions based on experimental extrapolations give S0. Our calculations give S=0.4 and a barrier height of 2.2 eV; the latter is in good agreement with experiment. © 1978 The American Physical Society.