Neutron Diffraction ? The Total Powder Pattern

Abstract

The value of the ordinate of a neutron powder pattern is expressed as the sum of Bragg scattering, due to the existence of an average lattice, and diffuse scattering, due to local deviations from the average lattice. In this form the calculated pattern can be refined by least squares methods against the observed pattern to give both average structural parameters and disorder parameters. Significant advantages over the use of only Bragg scattering for the determination of structural parameters are: (1) a powerful limit on the value of the temperature factor is imposed by the condition that neutrons removed from Bragg peaks must be accounted for in the diffuse scattering; (2) correlation between partially occupied sites can be found. The cross sections for Bragg and disorder scattering are given.