The energy and elastic constants of simple metals in terms of pairwise interactions

Abstract

Second order perturbation theory enables the author to write U, the energy of a simple metal, as a large volume dependent part F(V) plus a small term which is the sum over pairs of ions of the central interaction Phi (R; rho ), R being the ion-ion distance. It is noted that Phi is a density dependent pair potential; hence the additional argument. The physics of this representation is discussed. Expressions for the pressure P and bulk modulus B are derived. The author derives formulae and gives numerical results to show a violation of the Cauchy relations and a correction to the conventional lattice dynamical theory of B. Without reference to a particular model an estimate of this correction is obtained.