Prediction of ordering in binary transition-metal alloys

Abstract

A simple model is presented which can successfully predict ordering in binary transition-metal alloys. Rectangular electronic densities of states (DOS) for both ordered and disordered states are assumed, along with the invariance of the first four moments of the DOS upon ordering. The ordering energy Delta U can then be calculated independently of the nature of the crystal lattice. The ordering tendency given by the sign and magnitude of Delta U, is plotted in ordering maps as a function of concentration and d-band filling. Computed ordering maps are found to be in excellent agreement with those obtained by much more elaborate coherent potential calculations. The overwhelming majority of the ordered structures observed experimentally in transition-metal alloys fall within the predicted ordering regions in these maps.