[1] Univ Cambridge, Dept Chem, Unilever Ctr Mol Informat, Cambridge CB2 1EW, England
[2] Cambridge Univ Lib, Cambridge CB3 9DR, England
[3] Univ London Imperial Coll Sci Technol & Med, Dept Chem, London SW7 2AZ, England
[4] Univ London Imperial Coll Sci Technol & Med, ICT, High Performance Comp Unit, London SW7 2AZ, England