Phonon spectrum of YH3: Evidence for a broken symmetry structure - art. no. 100301

Total-energy calculations for YH3 indicate that small symmetry-breaking hyd rogen displacements can lower the total energy of the structure deduced fro m neutron powder diffraction (NPD) experiments on YD3. However, such displa cements were not observed in subsequent low-temperature NPD experiments. He re we present the results of parameter-free lattice dynamics calculations f or YH3. Comparison of the theoretical vibrational densities of states calcu lated for the HoD3 and broken-symmetry structures with the recently reporte d experimental spectrum determined by inelastic neutron scattering yields e vidence that symmetry lowering has in fact been seen.