  Hydrogen arranges at dislocations in palladium to form nanoscale hydrides,
changing the vibrational spectra. An ab initio hydrogen potential energy model
versus Pd neighbor distances allows us to predict the vibrational excitations
for H from absolute zero up to room temperature adjacent to a partial
dislocation and with strain. Using the equilibrium distribution of hydrogen
with temperature, we predict excitation spectra to explain new incoherent
inelastic neutron-scattering measurements. At 0K, dislocation cores trap H to
form nanometer-sized hydrides, while increased temperature dissolves the
hydrides and disperses H throughout bulk Pd.
