The dynamical process of the phase transition from VO2(M) to VO2(R)

The dynamical process of the metal-insulator transition, from VO2(M) to VO2(R), is studied in the framework of the dynamics theory. It is found that the thermal exciting of the Raman-active Ag mode with frequency of 212.7 cm-1 in the VO2(M) lattice drives the compound to be the VO2(R) lattice. The intermediate structures during the phase transition are revealed, from which we find that when the distortion of the atomic network away from its initial network in the M phase exceeds 60%, the system becomes metallic. At the moment, the monoclinic symmetry of the crystal remains still, but more V ions are dimerized. This strongly suggests that the dimerization of the V ions in the compound plays a critical role in the transition from the M phase to the R phase.