Pressure tuning of the charge-density wave in the halogen-bridged transition-metal solidPt2Br6(NH3)4

We report the pressure dependence up to 95 kbar of Raman-active stretching modes in the quasi-one-dimensional MX chain solid ${\mathrm{Pt}}_2$ ${\mathrm{Br}}_6$(${\mathrm{NH}}_3$ ${)}_4$. The data indicate that a predicted pressure-induced insulator-to-metal transition does not occur, but are consistent with the solid undergoing either a three-dimensional structural distortion or a transition from a charge-density wave to another broken-symmetry ground state. We show that such a transition can be well modeled within a Peierls-Hubbard Hamiltonian.