Abstract
A first-principles pseudopotential is derived which is optimized specifically for the case of a binary alloy. The potential is applied to calculate the structural, thermochemical and thermomechanical ground-state properties of the Li-Mg system. It explains successfully the variation of the lattice parameter and the bulk modulus with concentration, accounts very well for the crystal structure and the stability range of the alloy phases, and predicts the enthalpy of formation in good qualitative agreement with experiment. It is shown that local-environment effects should be considered for a calculation of ordering properties.