Inelastic neutron scattering, dynamics of atoms and novel material properties

Information on dynamics of atoms in solids is very important in microscopic understanding of material properties, such as phase transitions, thermal conductivity and super-ionic diffusion, and unusual phenomena like negative thermal expansion. Moving atoms can be probed by many radiations when they would cause a shift in their energy. Thermal neutrons are an ideal probe. So neutron inelastic scattering along with computer simulation, provide very useful tools to investigate the atomic dynamics. Atomistic simulations can be performed by the techniques of molecular dynamics simulation and quasiharmonic lattice dynamics. The latter technique is especially essential at low temperatures below the so-called Debye temperature when quantum mechanics is important. The molecular dynamics technique is immensely useful to study the structures and dynamical phenomena at high temperatures, near phase transitions, or away from equilibrium, stochastic dynamics, crystalline defects, amorphous materials, etc. We have investigated a variety of ionic solids especially with polyhedral network structures, namely, high-temperature superconductors, mineral silicates and other perovskite related structures, as well as negative thermal expansion materials, super-ionic conductors, etc. The talk will review some of these developments. (author)