Neutron energy loss measurements provide a powerful method of studying the modes of
vibration of hydrogen in metal lattices. The crosssection for neutron scattering is proportional
to the amplitude-weighted frequency distribution. Both the frequency distribution and the
amplitudeweighting function can be obtained from the interatomic force constants by the
standard methods of lattice dynamics. These calculations have been performed for rare
earth dihydrides and it is found that hydrogen-nearesthydrogen forces have to be introduced …