Phonons in Complex Materials

Dr. Bartomeu Monserrat, Department of Materials Science, University of Cambridge

Abstract:

Phonons in complex materials Phonons and their interactions play a key role in many physical properties of materials, from the heat capacity to electronic and thermal transport. The first principles calculation of phonons is well established for weakly correlated crystalline materials using density functional theory. However, the calculation of phonons and related properties presents a considerable challenge in more complex materials, for example in strongly correlated materials or in non-periodic materials.

In this talk, I will introduce a methodological development to efficiently calculate phonons in complex materials using finite differences. We combine the minimum nondiagonal supercell commensurate with a given phonon wave vector, together with the nonuniform sampling of the Brillouin zone, to dramatically reduce the computational cost of phonon calculations. As a result, we can efficiently evaluate phonons in complex materials. I will discuss a number of examples, including phonons in strongly correlated materials and in incommensurate non-periodic crystals.