Abstract

One of the major developments in computational science over the past decade and a half has been the rise of dynamical studies in materials science based on density-functional theory. This has enabled a new close-coupling of computational dynamics with experimental spectroscopy which can add value and impact to both.

I will discuss how dynamical properties of materials may be approached from the low-temperature crystalline or high-temperature disordered state by lattice dynamics or molecular dynamics methods respectively. Much simulation effort is devoted towards understanding the properties of materials used in engineered systems for energy conversion, transport and storage. First principles lattice dynamics calculations have revealed the existence of anharmonic “Rattler” modes in the layered thermoelectric material NaxCoO2, as a consequence of large period ordered superstructures. These lower the thermal conductivity nearly six-fold, and so increase the thermoelectric “figure of merit” by the same factor. I will also discuss dynamical disorder in the superionic conductor LiBH4, and show how only a full molecular-dynamics treatment is capable of describing the phase transition and superionic state. Even then, a further development of MD - ab initio non-equilibrium molecular dynamics – is required to model the Li ion transport in the high-temperature phase.