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Title: Atomistic simulation of calcite surfaces
Author: Kerisit, Sébastien N.
Awarding Body: University of Bath
Current Institution: University of Bath
Date of Award: 2004
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The aim of this thesis is to develop an atomistic model of the mineral-water interface taking calcium carbonate as an example. This model would enable us to gain insight into the microscopic processes involved in the growth and dissolution of minerals, In Chapter 1, major experimental and computational studies of calcite surfaces arc reviewed and the main topics of this thesis arc presented. Chapters 2 and 3 discuss the methodology used throughout this work. In Chapter 2, the potential model is explained in great detail. Chapter 3 gives an introduction to the computational techniques, namely energy minimisation and molecular dynamics, used throughout this study, together with a brief description of the density functional theory, also used in this thesis. Chapters 4 to 8 present the main results obtained during this project. In Chapter 4, energy minirnisations of the main low-index surfaces of calcite reveal that the {1014} surface is the most stable surface in both dry and hydrated conditions. In addition, it was found that the reaction of water with surface carbonate groups, which results in the dissociation of water molecules, would occur at step edges and defective surfaces rather than at the {1014} surface. In Chapter 5, a comparison of the surface energies obtained from electronic structure calculations with those described in the previous chapter shows that the relative energies are in very good agreement. Also, surface phase diagrams of three surfaces in contact with a gaseous phase suggest that calcium poor surfaces are the dominant terrninations under ambient conditions.In Chapter 6, potential parameters developed to model the interactions of carbonate surfaces with water are shown to also reproduce the structure and dynamics of the hydration shell of metal cations. This chapter also presents new potential parameters for modelling halide ions in solution. In Chapter 7, the free energy of adsorption of water on the {lOI4} surface is calculated and found to be small when compared to the enthalpy of adsorption, therefore implying a large entropy of adsorption. Also, it is shown that the free energy profiles of metal ions adsorbing on the surface are correlated with the solvent density. In Chapter 8, the distribution of ions near the surface, calculated from molecular dynamics simulations, is found to differ from the classical view of the electrical double layer. Finally, Chapter 9 gives a summary of the main results presented in this thesis
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available