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Title: Computer simulations of calcite
Author: Archer, T. D.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2004
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In this dissertation I have created and applied a parametric model for bulk carbonate materials. The new empirical model for carbonates is stable for a wide range of carbonate structures and reproduces experimental results with reasonable accuracy. To study the surface of calcite the ab initio code SIESTA has been used. New implementation has been introduced into the SIESTA code to allow the calculation of effective charges using the modern theory of polarisation. Using these charges the calculation of the long range electrostatic effects, which are removed by the zero electric field boundary conditions, have been introduced into the phonon methodology, reproducing the LO-TO splitting within the calculated phonon modes near the F-point. Furthermore the effective charges have been used in the calculation of the infrared intensity for each phonon mode. The SIESTA implementation of DFT relies upon the evaluation of electron density on a real-space grid. Such discretization of the real-space integrals introduces an oscillatory error in the energy and forces, with the periodicity of the real-space grid. A method for reducing this error has been introduced. The SIESTA code with the new methodology has been used to study bulk calcite, {211} calcite surface and the interaction of water with the {211} sur­face. The structure and phonon frequencies for the bulk match well with experimental values. The {211} surface has been calculated showing the response of the crystal in both distortion of the ion position and the electronic configuration. Surface relaxations and phonon frequencies show no symmetry breaking reconstruction of the calcite {211} surface. Calculation of the interaction of water molecules with the {211} surface predicts the optimum position for water on the surface.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available