High pressure studies of hard materials

The titanium suboxide Magneli phase Ti4O7 has a triclinic structure related to that of rutile TiO2. It has a semivalent Ti3.5+ state and thus is of interest for charge ordering. Previous work showed that first order transitions are present, one at 125-140 K and the second one at 150 K. No structural studies of any of the phases of Ti4O7 have been reported since 1984, despite renewed interest in the electronic, magnetic, and optical properties. The results of this study will provide definitive structures for the fundamental semivalent oxide Ti4O7, settling long running questions about the charge and orbital orders, and the associated orbital dimer array. Overall, this work will contribute to understanding of charge localisation and ordering in transition metal oxides.