High entropy alloys contain multiple elements in large proportions that make them prone to phase separation. These alloys generally have shallow enthalpy of mixing which makes the entropy contributions of similar magnitude. As a result, the phase stability of these alloys is equally dependent on enthalpy and entropy of mixing and understanding the individual contribution of thermodynamic properties is critical. In the overall vision of designing high entropy alloys, in this work, using density functional theory calculations, we elucidate the contributions of various entropies, i.e., vibrational, electronic and configurational towards the phase stability of binary alloys. We show that the contribution of electronic entropy is very small compared to the vibrational and configurational entropies, and does not play a significant role in the phase stability of alloys. The configurational and vibrational entropies can either destabilize or can collectively contribute to stabilize the solid solutions. As a result, even those systems that have negative mixing enthalpy can show phase instability, revealed as a miscibility gap; conversely, systems with positive mixing enthalpy can be phase stable due to entropic contributions. We suggest that including entropic contributions are critical in the development of theoretical framework for the computational prediction of stable, single-phase high entropy alloys that have shallow mixing enthalpies, unlike ordered intermetallics.

高熵合金包含大量的多种元素，这使其易于相分离。这些合金通常具有较浅的混合焓，这使得熵的贡献相似。结果，这些合金的相稳定性同样取决于混合的焓和熵，并且了解热力学性质的个体贡献至关重要。在设计高熵合金的总体视野中，在这项工作中，我们使用密度泛函理论计算，阐明了各种熵（即振动，电子和构型）对二元合金的相稳定性的贡献。我们证明，与振动和构型熵相比，电子熵的贡献很小，并且在合金的相稳定性中不发挥重要作用。构型和振动熵可能不稳定或可能共同有助于稳定固溶体。结果，即使那些具有负混合焓的系统也可能显示相不稳定性，表现为混溶性间隙。相反，由于熵的贡献，具有正混合焓的系统可以是相稳定的。我们建议，与有序金属间化合物不同，包括熵的贡献对于稳定的具有浅混合焓的单相高熵合金的计算预测的理论框架的发展至关重要。甚至那些具有负混合焓的系统也可能显示相不稳定性，表现为可混溶间隙。相反，由于熵的贡献，具有正混合焓的系统可以是相稳定的。我们建议，与有序金属间化合物不同，包括熵的贡献对于稳定的具有浅混合焓的单相高熵合金的计算预测的理论框架的发展至关重要。甚至那些具有负混合焓的系统也可能显示相不稳定性，表现为可混溶间隙。相反，由于熵的贡献，具有正混合焓的系统可以是相稳定的。我们建议，与有序金属间化合物不同，包括熵的贡献对于稳定的具有浅混合焓的单相高熵合金的计算预测的理论框架的发展至关重要。