Temperature- and pressure-induced transitions from the charge-density-wave (CDW) phase to the Mott-Hubbard (MH) phase in the quasi-one-dimensional Br-bridged Pd compound, [Pd(en) 2Br](Cn-Y) 2·H 2O (n = 4-9, and 12) (en: ethylenediamine, C n-Y: dialkyl-sulfosuccinate), were investigated by means of crystal-structure analyses and Raman spectroscopy. From the systematic evaluations of the bridging-bromine displacements δ reflecting the CDW amplitudes, the distance L between the neighboring two Pd ions, and the Raman frequency ωS of the symmetric Pd-Br stretching mode, we demonstrated that ωS is a good measure of the CDW amplitude. By scrutinizing the variations of ωS in the pressure-induced and the temperature-induced CDW-to-MH transitions, we discuss the nature of the CDW to- MH transitions in this category of materials.
- Charge density wave
- Extended Peierls-Hubbard model
- Mott-Hubbard phase
- Phase transition
- Raman spectroscopy