Inelastic neutron scattering from pyrope powder: experimental data and theoretical calculations

Time-of-flight (TOF) coherent inelastic neutron scattering measurements have been carried out at 14 and 30 K, on a powder sample of natural pyrope garnet [(Mg0.92Fe0.05Ca0.03)3Al 2Si3O12, space group Ia3d, Z = 8, a = 11.455(1) Å] from the Dora Maira Massif, Italian Western Alps, in order (i) to investigate its vibrational properties and (ii) to determine the contribution from component atoms to the one-phonon density of states, for clarifying the sources of some thermodynamic anomalies. An interatomic potential function has been modeled by simultaneous fitting to the structural, elastic and vibrational observables of the mineral. The developed potential has been employed to interpret the experimental inelastic neutron scattering patterns. The calculations have been performed within the framework of the lattice dynamics.