New approach in the study of hydrogen dynamics in metal hydrides by neutron transmission experiments

Abstract

We propose a new approach to the analysis of total cross-section measurements of hydrogen in metal hydrides, aimed at obtaining primary information about the dynamics of hydrogen in these compounds, including the characteristic frequencies and mean-square displacement of the proton. We use a simplified model to describe the hydrogen vibrational spectra and a translational effective mass to take into account the hydrogen diffusive motion. This approach is based on the splitting of the total incoherent cross-section in two well-defined terms: a quasi-elastic contribution – depending on the translational effective mass and the mean-square displacement of hydrogen atoms – and an inelastic contribution, related to the vibrational frequency spectra. In this work we present the starting approximations and develop the formalism involved in the analysis, illustrating its application through experiments performed on zircaloy-4, magnesium and niobium hydrides.