Pseudospin Clusters and Short-Range Correlations

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Abstract

Structural phase transformations constitute a major subject of investigation in thermodynamics of crystalline states. A partial displacement in the constituent molecule represented by an order variable is essential for describing structural changes. Although considered as primarily independent of the lattice structure, such an order variable in finite magnitude disrupts local symmetry in a crystal. Correlations of these variables between adjacent sites are responsible for their clustering, leading to a macroscopic symmetry change. Following Born and Huang, we consider clustered order variables in a short range to form condensates for minimal structural strains in the lattice. Consequently, a condensate is characterized by a specific wave vector for propagation in the lattice. In this chapter, we define pseudospins for binary order variables and discuss the nature of their correlations in short range.

Keywords

Order Variable Correlation Energy Classical Vector Structural Phase Transformation Constituent Molecule 
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Copyright information

© Springer Science+Business Media, LLC 2010

Authors and Affiliations

  1. 1.Department of PhysicsUniversity of GuelphGuelphCanada

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