Electronic structure of random alloys and the theory of ordering processes

We consider some of the approaches toward obtaining an understanding of alloy phase stability within the context of ab initio density functional theory. We show recent results of calculations, using the concentration functional theory of Gyorffy and Stocks, of the spinodal for PdcRh1-c alloys. We also show results for short-range order diffuse scattering patterns in AlcAg1-c which show that the intersite interactions change from clustering to ordering with increasing silver content. The implications of these results for the phase diagram of AlcAg1-c alloys and for Guinier-Preston zone formation in aluminium-rich alloys are briefly discussed. In conclusion, some conjectures about what the future might hold regarding first-principles theories of phase stability are made. (author) 22 refs., 4 figs