We develop and apply atomistic modelling approaches to a range of challenges in materials chemistry. We use high-level approaches to probe why materials adopt particular crystal structures – their detailed internal structure, including defects – their external form and surface structure and we seek to explain the origin of functional behaviour in materials. We focus on fundamental materials, like water ice, which is still revealing subtle properties that influence its physical properties. We also investigate materials with tremendous commercial importance, such as zeolites that are ubiquitous in petrochemical applications. As well as seeking to explain observed materials structures and properties, we also predict how materials can be tweaked at the atomic level, to increase their potency in catalysis, molecular separation and molecular storage.