MS26-P01 Polarisation via local ordering mechanisms Emma Wolpert (Department of Chemistry, University of Oxford, Oxford, United Kingdom) Alistair Overy (Department of Chemistry, University of Oxford, Oxford, United Kingdom) Peter Thygesen (Department of Chemistry, University of Oxford, Oxford, United Kingdom) Arkadiy Simonov (Department of Chemistry, University of Oxford, Oxford, United Kingdom) Mark Senn (Department of Chemistry, University of Warwick, Coventry, United Kingdom) Andrew Goodwin (Department of Chemistry, University of Oxford, Oxford, United Kingdom) x x (x, x, United Kingdom) x x (x, x, United Kingdom) x x (x, x, United Kingdom)email: emma.wolpert@chem.ox.ac.ukSystems containing correlated disorder are becoming more and more prevalent in materials science.1 Thus understanding and exploring the disorder-property relationship is becoming of greater importance. In our work2 we focussed on how aperiodic systems could lead to a macroscopic polarisation. Using classical Monte Carlo simulations, we study a simple statistical mechanical model from local displacements on the square and cubic lattices. Our model contains two key ingredients: a Kitaev-like orientation-dependent interaction between nearest neighbours, and a steric term that acts between next-nearest neighbours. Taken by themselves, each of these two ingredients drives its own form of local ordering to a non-polar disordered phase with a manifold of degenerate ground states. These phases are incapable of driving long-range symmetry breaking, despite the presence of a broad feature in the corresponding heat capacity functions. Instead each ingredient results in a "hidden" transition on cooling to two distinct types of local order. Remarkably, their intersection i.e. the ground state when both interaction contributions are invoked leads to a disordered, but polar, phase which has conceptual parallels to tetragonal BaTiO3 or KNbO3.3 These key ingredients could potentially be utilised in future material designReferences:

[1] Damasceno, P. F. et al. (2012). Science 337, 453–457.

[2] Wolpert, E. H. et al. (2018). Phys. Rev. B, 97, 134106.

[3] Senn, M. S. et al. (2016). Phys. Rev. Lett. 116, 207602.
Keywords: polarisation, correlated disorder