Geometry Optimisation with CASTEP

Chris Eames

This document is a basic introduction to the methodology of performing geometry optimisation calculations with the CASTEP program. It is not intended as a review of the ideas behind that methodology. Before approaching this guide the reader is strongly recommended to read a relevent review article (such as [1] or [2]) if they do not have the background knowledge.

The aim of this guide is to answer three questions;

• What structures can be geometry optimised and what types of geometry optimisation are there?
• What are the basic inputs to a calculation and how are they set up?
• What are the possible outputs of a calculation and how should they be interpreted?

We begin with a discussion of what occurs during a calculation and an outline of what the main considerations should be for the user. Some example calculations are presented at the end to show how it all fits together.