We review various simplified models that have been advanced to describe layering (complexion) transitions at grain boundaries in multicomponent solids. In particular, we first outline lattice-gas, off-lattice atomistic and thermodynamic models that have been employed to investigate phase-like behavior at segregated grain boundaries. The results of these investigations are summarized in the form of complexion diagrams in different thermodynamic planes, and we highlight important features of these diagrams, such as complexion transition lines and critical points. Finally, we describe current issues and provide a future outlook.

中文翻译：

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晶界处的分层过渡

我们回顾了已简化的各种简化模型，这些模型描述了多组分固体中晶界处的分层（复杂化）过渡。特别地，我们首先概述晶格气体，晶格外原子和热力学模型，这些模型已被用来研究偏析晶界处的相态行为。这些研究的结果以不同热力学平面中的肤色图形式进行了总结，我们重点介绍了这些图的重要特征，例如肤色转变线和临界点。最后，我们描述当前问题并提供未来展望。