Dynamic Processes and Disorder in Materials as seen by Temperature-Dependent Diffraction Experiments

Abstract

The primary results of crystal structure determinations are long lists of uninformative numbers: tables of atomic coordinates and anisotropic displacement parameters (ADP’s). To be useful the numbers need to be transformed. Atomic coordinates are easily converted into interatomic distances, angles, conformational descriptors and other quantities of interest in structural chemistry. Atomic displacement parameters which encode information on motion and disorder, are more difficult to decipher. This is because interatomic or correlation ADP’s which describe the coupling of atomic displacements, are lost in Bragg diffraction. Here it is shown how information on correlated atomic displacements can be retrieved from the temperature dependence of ADP’s.