1. Canadian Neutron Beam Centre, Station 18, Chalk River Laboratories, Chalk River, Ontario K0J 1J0, Canada, ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, United Kingdom, Institut für Mineralogie Abteilung Kristallographie, Johann Wolfgang Goethe−Universität, Senckenberganlage 30, D-60054 Frankfurt, Germany, and Accelrys Incorporated, 334 Science Park, Cambridge CB4 0WN, United Kingdom