1ST-PRINCIPLES CALCULATION OF THE AG-CU PHASE-DIAGRAM

Total-energy band calculations based on the augmented-spherical-wave method are used to determine the binding curves of the elements and of selected compounds in the Ag-Cu system. The calculated total energies, together with vibrational free energies determined by a Debye-Gruneisen analysis of the binding curves and configurational entropies determined by the cluster variation method, are used to calculate the solid-state portion of the Ag-Cu phase diagram. The solubilities at both ends of the phase diagram, calculated with no adjustable parameters, are in excellent agreement with experiment. For the Ag-Cu system, it is shown that local volume relaxation effects are very important and that significant improvement in the calculated phase diagram is obtained by including vibrational free energies.