1. School of Chemistry, University of Edinburgh, David Brewster Road, Edinburgh EH9 3FJ, Scotland
2. Centre for Science at Extreme Conditions, University of Edinburgh, Peter Guthrie Tait Road, Edinburgh EH9 3FD, Scotland
3. Global Lubricants Technology Research and Innovation, BP International Limited, Technology Centre, Whitchurch Hill, Pangbourne, Reading RG8 7QR, England