1. Numerical Algorithms Group Ltd., Oxford OX2 8DR, UK
2. Computational Science and Engineering Department, STFC Daresbury Laboratory, Cheshire WA4 4AD, UK
3. Department of Chemistry, Imperial College London, London SW7 2AZ, UK
4. Computational Science and Engineering Department, STFC Rutherford Appleton Laboratory, Oxfordshire OX11 0QX, UK
5. The University Chemical Laboratory, Lensfield Road, Cambridge CB2 1EW, UK