Modelling nanocomposite dielectrics - polarization and inclusions at the atomic scale

Abstract

This thesis details the computational investigations into molecular-nanoparticle based nanocomposite dielectric candidate materials. Mainly silver-based nanoparticles under 32 atoms in metal-oxide and polymer model materials to understand how encapsulation affects local and bulk dielectric function and how to model such candidates. Chapter 1 introduces the ideas behind molecular nanoparticles (MNP) and functional dielectrics at the sub-100nm range. Emphasis on bridging gaps present in the literature at present and potential novel uses between atomic-doping and traditional larger nanoparticles. Chapter 2 delves into theory and background as this is an entirely theoretical and computational thesis. An explanation of both static and optical dielectric starting from electronic structure and ending in a comparison of methods. Further computational details provided in relevant next chapters. Chapter 3 contains details of the major topic of this thesis: How to model a molecular nanoparticle inclusion in a solid-state dielectric. The candidates of Ag inclusion and MgO candidate metal-oxide were modelling using Car-Parinello Molecular Dynamics to obtain a size and shape correlation in nanoparticles as well as some guidelines for computing charge distribution and quantum of polarization effects. Chapter 4 contains details of the optical polarization of Ag-PVDF nanocomposites with a focus on interacting particles and non-homogeneity in MNP distribution. This project aimed to move towards a more realistic model with two nanoparticles interacting at various distances. Chapter 5 is an attempt to push the boundaries of highly detailed molecule-level polarization calculations and a discussion on their usefulness without experimental backing. Chapter 6 summarizes this thesis followed by some QuantumEspresso code and parameters used.Graduat