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Kinetics of Surface Reconstruction

The surfaces of crystalline materials are prone to reconstruct in response to a variety of intrinsic and/or extrinsic driving forces (mitigation of dangling bonds, minimisation of surface stress, accommodation of adsorbed species, etc) and these have been catalogued and explained in some depth. Receiving far less attention, however, the kinetics of reconstruction are still subject to dispute. In some cases, distinctly non-linear behaviour has been observed with respect to adsorbate coverage, leading to oscillatory and/or chaotic phenomena, but the underlying cause of the non-linearity remains obscure. Fully understanding the fundamental processes of reconstruction, and especially capturing the potentially crucial role of surface steps and defects, will require the computational simulation of large systems over long time periods. To that end, this project will make use of the Adaptive Kinetic Monte Carlo code known as DL_AKMC, which incorporates model potentials to permit the necessary length- and time-scales to be addressed. First-principles density functional theory (implemented in the CASTEP code) will then be targeted at key mechanistic steps in the process of reconstruction, both as a test of accuracy for the model potentials and as a means of explaining the physics of the process in terms of electronic structure.