Crystalline thin films of silica: modelling, structure and energetics

Abstract

The static structural and energetic properties of thin crystalline films (∼two dimensional bilayers) of silica, SiO2, are modelled. Two potential models are considered in which the key interactions are described by purely harmonic terms and more complex electrostatic terms, respectively. The relative energetic stability of two potential crystalline forms, which represent alternative ways of tiling two dimensional space, is discussed. Coherent and incoherent distortions are introduced to the simulated crystals and their effects considered in terms of the ring structure formed by the Si atoms. The spatial relationship between distorted rings is analysed. An experimentally-observed single crystalline configuration is considered for comparison throughout.

Constructing bilayers with tuneable ring statistics and topologies

“…In order to simulate bilayer systems in two dimensions, a suitable potential model is needed which captures the essential physics of the system: the local triangular environment of the [SiO 3 ] units and the varying relative energies of rings of different sizes. The model used here is modified from a relatively simple potential used in allatom bilayer calculations [7,18]. Each [SiO 3 ] unit has a harmonic potential acting between all three Si-O pairs, and the three nearest-neighbour O-O pairs, given by:…”