Rigid unit modes in framework silicates
Rigid unit modes in framework silicates
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DOI：
10.1180/minmag.1995.059.397.07
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发表时间：
1995-12-01
影响因子：
2.7
通讯作者：
Hammonds, KD
中科院分区：
文献类型：
--
作者：
Dove, MT;Heine, V;Hammonds, KD
我们描述了一个框架硅酸盐模型，其中SiO4（和AlO4）四面体被视为完全刚性和自由连接。从这个模型中，我们能够识别出结构的低能量变形模态，我们称之为刚性单元模态。这些模式可以作为软模式，允许在相变时容易失真。我们讨论了将与候选软模式一起作用于相变的三种力，以确定哪一种刚性单元模式实际上会沉淀相变，并通过详细讨论石英、白晶石和方英石的相变来说明这些想法。该模型还可用于估计转变温度，该理论强调了四面体刚度的重要作用。
We describe a model for framework silicates in which the SiO4 (and AlO4) tetrahedra are treated as perfectly rigid and freely jointed. From this model we are able to identify low-energy modes of distortion of the structure, which we call Rigid unit modes. These modes can act as soft modes to allow easy distortions at phase transition. We discuss three forces that will operate at a phase transition in conjunction with the candidate soft modes to determine which of the rigid unit modes will actually precipitate a phase transition, and illustrate these ideas by detailed discussions of the phase transitions in quartz, leucite and cristobalite. The model can also be used to estimate the transition temperature, and the theory highlights an important role for the stiffness of the tetrahedra.