Abstract

Monoclinic, orthorhombic, and tetragonal models are proposed for the M₅C₄ superstructures of nonstoichiometric cubic transition metal MC_y carbides on the basis of symmetry analysis, the concept of a disorder–order transition channel, and a distribution function. Each of the disorder–order transition channels related to the formation of these model superstructures includes four superstructural vectors, which are the rays of non-Lifshitz stars {k₁}, {k₂}, or {k₄}. The distribution functions of carbon C atoms over the sites of the M₅C₄ superstructures are calculated. The estimated probabilities of existence of vacancy pair configurations in the superstructures under study suggest that the tetragonal M₅C₄ superstructure is the most stable of them.

中文翻译：

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M 5 C 4相—新型碳化物上层结构

摘要

基于对称性分析，无序过渡通道和分布函数的概念，为非化学计量立方过渡金属MC _y碳化物的M ₅ C ₄上层结构提出了单斜，正交或四边形模型。与这些模型超结构的形成有关的每个无序阶跃转换通道都包括四个超结构矢量，它们是非Lifshitz星{ k ₁ }，{ k ₂ }或{ k ₄ }的射线。碳C原子在M ₅ C ₄位置上的分布函数计算上层建筑。在研究中的上层建筑中，空位对构型存在的估计概率表明，方形M ₅ C ₄上层建筑是最稳定的。