In recent years, total energy calculations based on the local density approximation (LDA) have begun to find applications in materials science [1]. In the context of the present symposium, the most relevant application is to the calculation of total and relative energies of ordered alloy phases and their mixing enthalpies. The first-principles LDA approach is now taking over from tight-binding or simple empirical schemes in providing input to phase diagram calculations, for example, using Connolly-Williams inversion [2]. We wish to make two points in our contribution to the symposium.