Lattice effects in solids under hydrostatic pressure by neutron pair density function analysis

Abstract

Applications of the atomic pair density function, PDF, as a tool for determining short to intermediate range distortions in crystalline solids has gained momentum in recent years because of increased recognition of the significance of lattice effects to the intrinsic properties of materials. The analysis is carried out without assuming lattice periodicity as is commonly done with ordered solids since, by definition, local effects are aperiodic. Despite improvements on its accuracy by using synchrotron radiation and pulsed neutron sources that significantly reduce statistical error, its use has been limited on results from ambient conditions or as a function of temperature. This is because systematic errors are difficult to determine especially in high background environments such as with pressure measurements. Experiments of this kind can be quite useful, however, and for this reason a procedure is described in this paper for extracting local atomic information using real-space analysis under pressure. Although the corrections are first order approximations, the accuracy is comparable to other simpler experimental geometries.