  The anharmonic phenomena in Zirconium Hydrides and Deuterides, including
{\epsilon}-ZrH2, {\gamma}-ZrH, and {\gamma}-ZrD, have been investigated from
aspects of inelastic neutron scattering (INS) and lattice dynamics calculations
within the framework of density functional theory (DFT). The observed multiple
sharp peaks below harmonic multi-phonon bands in the experimental spectra of
all three materials did not show up in the simulated INS spectra based on the
harmonic approximation, indicating the existence of strong anharmonicity in
those materials and the necessity of further explanations. We present a
detailed study on the anharmonicity of zirconium hydrides/deuterides by
exploring the 2D potential energy surface of hydrogen/deuterium atoms, and
solving the corresponding 2D single-particle Schrodinger equation to get the
eigenfrequencies. The obtained results well describe the experimental INS
spectra and show harmonic behavior in the fundamental modes and strong
anharmonicity at higher energies.
