STRUCTURE MAPS FOR CONSTRAINED STRUCTURES AT HIGH PRESSURES FROM POWDER DIFFRACTION: Practical Considerations and Case Studies

摘要

Structure maps follow the evolution of unit cell symmetry and elements of crystal structure such as site occupancies, interatomic distances and angles as a function of composition, temperature, pressure and other variables. Diffraction data provide a relatively unambiguous means of deriving atomic level information for the construction of these maps, which may be related to phase diagrams. For many high-pressure studies at room temperature however, phases often persist in a metastable state far outside their stability fields or may be greatly affected by deviatoric stress. So, maps detailing changes in phase may bear little resemblance to equilibrium phase diagrams; their purpose is to follow a material's response at the atomistic level to changes in composition and/or environment, and ultimately to relate these to changes in physical properties.