Small-angle neutron scattering measurements of hydrogen and deuterium trapped at dislocation defects in deformed single-crystalline Pd were performed at 15, 100 and 200K at total interstitial solute concentrations of order 10-3. This work supports recent incoherent inelastic neutron scattering measurements of the vibrational density of states of trapped hydrogen under similar concentration-temperature conditions (Heuser et al., 2008). The measured net absolute macroscopic differential scattering cross sections were fitted with a cylindrical form factor representing solute-decorated dislocation line segments. Generally, very little difference in the measured cross sections was observed with temperature for a given solute type, while a significant change was observed between hydrogen- and deuterium-loaded samples. The latter difference was understood within a cross-section model that takes into account the local lattice dilatation associated with solute segregation at dislocations. The application of the model cross section to the net PdH0.0013 small-angle neutron scattering response yields an effective trapping radius of R ∼10Å and dislocation density of ρd~1010/cm2. Analysis of the small-angle neutron scattering response allowed the local trapped solute concentration (∼0.5[H]/[Pd]) and volumetric dilatation (Δν/Ω ∼1.1) to be determined with the constraint that the system locally satisfies the known lattice expansion of Pd hydride (i.e., Vegard's law).

Small-Angle Neutron Scattering Measurements of Hydrogen and Deuterium Trapping at Dislocations in Deformed Single-Crystalline Pd at Low Temperature. B.J.Heuser, H.Ju: Physical Review B, 2011, 83[9], 094103