Project Title: Modelling Negative Thermal Expansion in Ruddlesden-Popper Oxides
Supervisors: Dr. Mark Senn. Dr Arash Mostofi and Dr Nicholas Bristowe
Most materials expand with increasing temperature therefore those which contract, that is to display negative thermal expansion (NTE), are interesting. Understanding the mechanism behind this rare property is not only of academic interest but may pave the way to developing materials with controllable thermal expansion. My research focuses on understanding the origins of uniaxial-NTE (NTE along one axis) in a class of Ruddlesden-Popper oxides (which are layered perovskite-like materials) through firstprinciples simulations. This involves identifying the lattice vibrational modes (phonons) responsible for NTE in this system, understanding why NTE occurs in certain systems but is generally rare amongst perovskite materials and investigating methods of controlling the level of NTE, for example through chemical and physical effects, to help design materials with controllable thermal expansion.