Symmetry-adapted configurational modelling of fractional site occupancy in solids
Symmetry-adapted configurational modelling of fractional site occupancy in solids
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DOI：
10.1088/0953-8984/19/25/256201
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发表时间：
2007-06-27
影响因子：
2.7
通讯作者：
de Leeuw, N. H.
中科院分区：
文献类型：
--
作者：
Grau-Crespo, R.;Hamad, S.;de Leeuw, N. H.
提出了一种方法，该方法减少了在固体中模拟位置无序时要计算的占位配置的数量，通过利用晶格的晶体对称性。在这种方法中，当两种构型通过等距操作相关时，它们被认为是等价的;可能的等距变换的试验列表由父结构中的对称算子组提供，其用于通过原子替换生成所有构型。我们已经适应了方程的构型统计操作在减少的构型空间的独立配置。在这个空间中的每一个组态的特征在于它的约化能量，这不仅包括它的能量，而且还包括它在完整组态空间中的简并度通过熵项的贡献。本文介绍了一个新的计算机程序SOD（占位无序），它可以对具有任意对称性和任意大小超原胞的体系进行这种分析。作为一个案例研究，我们使用的铁锑氧化物FeSbO（4）中的阳离子分布，在那里我们也介绍了一些一般的考虑，在顺磁系统中的占位无序的建模。
A methodology is presented, which reduces the number of site- occupancy configurations to be calculated when modelling site disorder in solids, by taking advantage of the crystal symmetry of the lattice. Within this approach, two configurations are considered equivalent when they are related by an isometric operation; a trial list of possible isometric transformations is provided by the group of symmetry operators in the parent structure, which is used to generate all configurations via atomic substitutions. We have adapted the equations for configurational statistics to operate in the reduced configurational space of the independent configurations. Each configuration in this space is characterized by its reduced energy, which includes not only its energy but also a contribution from its degeneracy in the complete configurational space, via an entropic term. The new computer program SOD (site- occupancy disorder) is presented, which performs this analysis in systems with arbitrary symmetry and any size of supercell. As a case study we use the distribution of cations in iron antimony oxide FeSbO(4), where we also introduce some general considerations for the modelling of site- occupancy disorder in paramagnetic systems.