The supercell approach to first-principles calculations of an alloy's full phonon spectrum is computationally expensive. It is therefore rarely used for calculating temperature dependent free energies of alloy phases or for calculating alloy phase diagrams. Amid the wider acceptance of uncertainty evaluation and the use of more efficient methods for materials design, the supercell approach is revisited and a simpler and more computationally efficient approximation is proposed. The new method is then used to calculate the Cr-Ni temperature dependent thermodynamic properties and phase diagram, resulting in predictions that are in good agreement with previous thermodynamic assessment. The new approach can facilitate accurate and rapid CALPHAD thermodynamic assessments of multi-component systems.

用于合金全声子谱的第一性原理计算的超级单元方法在计算上昂贵。因此，很少用于计算合金相随温度的自由能或用于计算合金相图。在不确定性评估得到更广泛的接受并在材料设计中使用更有效的方法的同时，重新讨论了超级单元方法，并提出了一种更简单，计算效率更高的近似方法。然后将新方法用于计算Cr-Ni温度相关的热力学性质和相图，得出的预测结果与以前的热力学评估非常吻合。新方法可以促进对多组分系统进行准确，快速的CALPHAD热力学评估。