High-pressure structural investigation of the spin-Peierls compound TiOCl.

TiOCl is a S=1/2 layered Mott insulator which displays a spin-Peierls state at low-temperatures involving the dimerization of the Ti ions. Although carrier localization is expected to be weak, it has proven difficult to dope charges in the system through partial chemical substitution. To explore if TiOCl could instead host a bandwidth-driven insulator-to-metal transition under external pressure, we investigated the crystal structure at pressures up to 17 GPa by means of powder and single crystal synchrotron x-ray diffraction in diamond anvil cells.