Calculations of the structural properties of cubic zinc sulfide

We report the results of first-principles pseudopotential total-energy calculations of the structural properties of cubic zinc sulfide. We show that, for a reasonable description of the properties of this material, the zinc 3d electrons may be incorporated within the pseudopotential as core electrons, provided that nonlinear core exchange-correlation corrections are included. We point out that such core corrections contribute nontrivial terms to the forces and stress and give explicit formulas for these within the momentum-space representation.