Solid solutions occur when multiple chemical species share sites of a common crystal lattice. Although the single site occupation is random, chemical interaction preferences bias the occupation probabilities of neighboring sites, and this bias reduced the entropy of mixing below its ideal value. Sufficiently strong bias leads to symmetry-breaking phase transitions. We apply the cluster variation method to explore solid solutions on body centered cubic lattices in the context of two specific compounds that exhibit opposite ordering trends. Employing density functional theory to model the energetics, we show that CuZn exhibits an order-disorder transition to the CsCl prototype structure, while AlLi instead takes the NaTl prototype structure, and we evaluate their temperature-dependent order parameters, correlations and entropies.

当多个化学物种共享同一晶格的位点时，就会发生固溶。尽管单个站点的占用是随机的，但化学相互作用的偏好使相邻站点的占用概率发生偏差，并且这种偏差将混合熵降低到其理想值以下。足够大的偏置会导致对称破坏的相变。我们应用聚类变分方法在两个特定化合物呈现相反的有序趋势的背景下探索体心立方晶格上的固溶体。利用密度泛函理论对能量学进行建模，我们表明CuZn表现出向CsCl原型结构的有序无序过渡，而AlLi取NaTl原型结构，并且我们评估了它们的温度依赖性有序参数，相关性和熵。