Fictive associates are widely used to describe and model liquid phases with strong ordering trends. However, little evidence is known about the assumed associates in most cases. In the present work, an ab initio molecular dynamics (AIMD) study is employed to investigate the characters of the Ba-Bi liquid, in which associates have been assumed in existing thermodynamic modeling. It is found that in the Ba rich melt, the Bi atoms are almost completely surrounded by Ba atoms. The Bi-centered coordination polyhedrons are strongly associated to crystalline structures of Ba5Bi3 and Ba4Bi3 with a longer lifetime than other polyhedrons during the AIMD simulations. In addition, these Bi-centered polyhedrons in Ba rich melt connect with each other through vertex, edge, face, and/or bipyramid sharing to form medium range orders (MRO). In the Bi rich melt, the Ba-centered polyhedrons also form MROs, but they are both structurally and compositionally diverse with a shorter lifetime. These findings from AIMD study provide evidences that there exist a strongly ordering Ba4Bi3 associate and a weakly ordering BaBi3 associate in the Ba-Bi liquid. The predicted enthalpy of mixing in the liquid agrees well with the results by the CALPHAD modeling in the literature.

中文翻译：

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具有强有序趋势的 Ba-Bi 液体中缔合物的从头分子动力学探索

虚拟关联被广泛用于描述和建模具有强烈排序趋势的液相。然而，在大多数情况下，关于假定的同事的证据知之甚少。在目前的工作中，从头分子动力学 (AIMD) 研究被用来研究 Ba-Bi 液体的特征，其中在现有的热力学模型中已经假设了关联物。发现在富 Ba 熔体中，Bi 原子几乎完全被 Ba 原子包围。在 AIMD 模拟过程中，Bi 中心配位多面体与 Ba5Bi3 和 Ba4Bi3 的晶体结构密切相关，其寿命比其他多面体更长。此外，富 Ba 熔体中的这些 Bi 中心多面体通过顶点、边缘、面和/或双锥共享相互连接，形成中阶 (MRO)。在碧富融，以 Ba 为中心的多面体也形成 MRO，但它们在结构和组成上都不同，寿命较短。AIMD 研究的这些发现提供了证据，证明在 Ba-Bi 液体中存在强有序的 Ba4Bi3 缔合物和弱有序的 BaBi3 缔合物。液体中的预测混合焓与文献中 CALPHAD 建模的结果非常吻合。