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Title: Development and application of atomistic force fields for ionic materials
Author: Sarsam, Joanne
ISNI:       0000 0004 2752 7566
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2013
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In the field of molecular dynamics (MD), the time evolution of a set of interacting atoms is determined by integrating their equations of motion using Newton’s Second Law. By using efficient potentials that capture the essential physics of a material, the properties of systems containing tens of thousands of atoms can be accurately modelled. This thesis describes three substantial developments in the science and simulation of ionic materials. In the opening chapters, we provide an introduction to the field of atomistic simulation, covering the theory and methods used in both classical molecular dynamics and density-functional theory (DFT). The use of DFT calculations in the parametrisation of force fields for molecular dynamics is described, and we discuss how the software used for MD and potential parametrisation has been radically overhauled and made more efficient and user friendly during the course of this work. We then study aluminium oxide, and develop a new potential which is faster and simpler than the current state of the art alumina potentials. The new potential is tested and found to accurately describe a range of physical properties. The potential is then applied to the study of intrinsic defects in alumina. Finally, we attempt to improve our description of heterogeneous ionic materials by developing and implementing a coupled charge-equilibration and polarisable ion model applicable to non-molecular systems. A review of the existing literature on the subject is made, before we describe the mathematical and physical reasoning behind our new implementation. Our method is found to be numerically accurate, and is subsequently applied to the study of defects and surfaces in magnesium oxide.
Supervisor: Tangney, Paul ; Finnis, Mike Sponsor: Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral