Local Structure and Dynamics in Framework Materials

To a large extent, crystallography has trained us to think of the structure of materials in terms of a set of atoms repeated according to a crystallographic unit cell. However, it is often the local deviations from this average, repeating structure that are most strongly implicated in a range of interesting and useful physical phenomena. For example, transverse vibrational motion gives rise to negative thermal expansion in particular framework materials, correlated ferroelectric displacements produce polar nano-regions in relaxor ferroelectrics, and magnetic structure transitions in metal oxides develop from localised spin ordering within the spin-disordered (paramagnetic) matrix of high-temperature phases.As such, the development of techniques capable of probing this local structure and the advancement of our understanding of the relationship between local structure and function are key problems in the physical sciences.The general aim of this proposal is to use a combination of computational and experimental techniques to study how local variations in average structure can produce interesting physical behaviour, with particular emphasis on the physical properties of framework materials: colossal magnetoresistance perovskites, superconducting cuprates, negative thermal expansion materials, magnetic phases (three-dimensionally ordered, low-dimensional systems and spin-liquids) and ultra-flexible framework structures.