Effect of Strong Neutron Absorption on Texture and Diffraction Data Analysis

Abstract

The impact of strong neutron absorption on data analysis and the comparison of two different absorption corrections for neutron diffraction data implemented in the GSAS Rietveld code are the foci of this work. We investigated the effect of absorption on the texture and the thermal motion parameter for rolled elemental foils. The orientation distribution functions (ODF) of rolled foils of dysprosium and erbium metals were determined from neutron time-of-flight data patterns collected on HIPPO at LANSCE. Both Dy and Er are strong absorbers for thermal neutrons with absorption cross-sections of 994 barns for Dy and 159 barns for Er at l = 1.8 Å. Various stacks of foils of each material, along with combinations of absorbing and less-absorbing foils, were measured. The patterns were analyzed using the GSAS options for Debye-Scherrer and linear absorption models, as well as without an absorption correction. Discrepancies between refined and expected “true” values of crystallographic parameters if absorption is not taken into consideration are discussed.