## Overview

Density-functional theory (DFT) is a quantum-mechanical theory that allows the properties of materials to be calculated from first principles or *ab initio* i.e. without making any prior assumptions about how the system under study should behave. This means it can even predict the properties of materials that have not yet been made. DFT is popular because it is sufficiently accurate for many purposes at a computational cost that is relatively cheap.

The computational cost of conventional DFT calculations scales as the cube of the system-size, limiting traditional methods to a few hundred atoms. My research focuses on the development of linear-scaling methods, their implementation within the ONETEP code and their application to the study of nanoparticles and biological systems in particular. A distinctive feature of the ONETEP method is the optimization of local orbitals (as shown in a barium titanate crystal above) in a manner equivalent to the plane-wave pseudopotential method used in the most popular conventional DFT methods.

## Collaborators

Professor Peter Haynes of Materials and Physics, and Dr David Rugg of Rolls-Royce plc., Imperial College London, This is a TSM-CDT PhD project on the fundamentals of cold dwell fatigue in titanium, for which the student is Adam Ready., 2013

## Guest Lectures

Linear-scaling density-functional theory: from fundamental principles to practical applications, Conference on Computational Physics, Gatlinburg TN, USA, 2011

Going to greater lengths: large-scale quantum simulations with linear-scaling density-functional theory, Competence Centre for Computational Science Seminar, University of Basel, Switzerland, 2011

Linear-scaling density-functional theory with the ONETEP code, Psi-k Conference, Berlin, 2010

Optimized local orbitals from linear-scaling density-functional theory calculations, American Physical Society March Meeting, Portland, 2010

ONETEP: linear-scaling DFT with local orbitals and plane waves, International Symposium of Electronic Structure Calculations, Tokyo, 2009

ONETEP: linear-scaling DFT with local orbitals and plane waves, Computational Materials Science Group Annual Meeting, Daresbury Laboratory, 2009

Future directions in electronic structure methods, Workshop on Density Functional Methods for Experimental Spectroscopy, Oxford, 2009

## Research Staff

## Research Student Supervision

Avraam,PW, Determining the charge distribution in polar semiconducting nanorods

Corsini,N, Pressure-induced structural transformations in nanomaterials

Nerl,HC, Cellular uptake and long-term fate of multi-walled carbon nanotubes

Poole,T, Calculating derivatives with quantum Monte Carlo

Poole,T, Force fields for carbon nanostructures via algorithmic differentiation

Ratcliff,LE, Calculating experimental spectra using linear-scaling density-functional theory

Ready,A, Point and planar defects in titanium

Zuehlsdorff,T, Theory and simulation of metal/semiconductor nanoparticle interfaces for solar energy storage