Activity coefficients for dilute solid solutions of Al in Ni

We present a method for predicting activity coefficients in dilute binary solid solutions from first principles and apply it to Al in Ni. Accurate results require knowledge of the temperature dependencies of both enthalpy and entropy: with the latter being dominant. The activity coefficient of Al varies by 15 orders of magnitude over 400 K ⩽ T ⩽ 1700 K: whereas that for Ni only varies by <4%. Available experimental data are consistent with these results.