Inelastic Neutron Scattering, Dynamics of Atoms and Novel Material Properties

We review our research on properties of two important functional materials in which dynamics plays an essential role, namely, fast-ion conductors and negative thermal expansion materials. We bring out the underlying role of the lattice dynamics in terms of the soft phonon modes in both cases. Then, using molecular dynamics simulation we show the mechanism of the fast-ion conduction that occurs at about 0.8 times the overall melting temperature in Li2O, UO2 and ThO2. We obtain numerical measures of the phonon anharmonicity from neutron-inelastic experiments and also lattice dynamics computations and quantitatively derive the negative expansion coefficient in several crystalline materials that is found to match well with direct diffraction measurements.