Institution: | a Department of Physics, University of Otago, Private Bag 56, Dunedin, New Zealand b Department of Physics, The Blackett Laboratory, Imperial College of Science, Technology and Medicine, Prince Consort Road, London SW7 2BW, UK c Computational and Theoretical Materials Sciences Group (CATMAS), Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, PA 16802-6812, USA |