3.1 Introduction

In this chapter, the principal ideas behind Quantum Monte Carlo methods are outlined. The theory of Monte Carlo integration is presented, and overviews given of the variational Monte Carlo method and the more sophisticated and accurate diffusion Monte Carlo method. These methods are both applications of Monte Carlo integration and form the basis for most of the calculations in this thesis.

Efficient implementation of these methods is critical. Inefficiencies increase computational overheads and effectively limit the size of system and statistical accuracy that may be obtained. Although some details and suggestions for efficient calculations are given, full details of application of the methods to electronic structure problems and their implementation are presented in the following chapter.