Computational Quantum Many-Body Theory

Liquids and solids consist of large numbers of atoms joined together by chemical bonds. Chemical bonds are formed by electrons which congregate in the regions between atoms because they are strongly attracted to the two neighbouring nuclei. Understanding the behaviour of the electrons in liquids and solids is the key to understanding chemical bonding, electrical conduction, and the optical properties of materials such as their colour or refractive index.In our research we use computational techniques to predict the properties of liquids and solids. Our principal goal is to study interesting and technologically important areas of the physics and chemistry of liquids and solids, starting from the level of the individual electrons. The behaviour of electrons is described by the quantum mechanical Schrodinger equation which, unfortunately, is very difficult to solve because the electrical forces between the electrons inextricably link their behaviour.In our research we start from a mean field picture in which the electrons move independently, and then we build in the correlations between the motions of electrons, which gives us an accurate technique for solving the Schrodinger equation. In one branch of our work we use Monte Carlo methods, which are based on random sampling, and in the other branch we use perturbation theory in which the correlations are introduced as corrections to the mean field behaviour. Here we propose using these computational methods to study a variety of problems in magnetic materials, the optical properties of matter, the behaviour of the antiparticle of the electron (the positron) in matter, the behaviour of electrons in small structures such as quantum dots and quantum wires and the properties of molecules bonded to solid surfaces.