First-principles prediction of the phase stability of high-entropy oxides

The fundamental thermodynamic driving forces enabling the formation of high-entropy oxides (HEOs) are not clearly understood. Since their discovery by Rost et al. [1], studies of the stability of HEOs have primarily focused on the role of ideal mixing entropies with comparatively little attention paid to the configurational influence of mixing enthalpies. In a recent paper, Bokas et al. [2] presented a model capable of predicting the mixing enthalpies of high-entropy alloys from the mixing enthalpies of their constituent binaries. Herein, we apply and further develop this methodology to HEOs by parameterizing a regular solution model using the mixing enthalpies of pairs of constituent end members. Using this model, one can identify HEO compositions most thermodynamically amenable to the formation of solid solutions. This method is tested on two systems of interest: Sr(Ti,V,Nb,Cr,Mo,W)O3 perovskites and (Fe,Co,Ni,Cu,Zn)Al2O4 spinels.