Correlation-assisted phonon softening and the orbital-selective Peierls transition in VO2

To explore the driving mechanisms of the metal-insulator transition (MIT) and\nthe structural transition in VO2, we have investigated phonon dispersions of\nrutile VO2 (R-VO2) in the DFT and the DFT+U (U : Coulomb correlation) band\ncalculations. We have found that the phonon softening instabilities occur in\nboth cases, but the softened phonon mode only in the DFT+U describes properly\nboth the MIT and the structural transition from R-VO2 to monoclinic VO2\n(M1-VO2). This feature demonstrates that the Coulomb correlation effect plays\nan essential role of assisting the Peierls transition in R-VO2. We have also\nfound from the phonon dispersion of M1-VO2 that M1 structure becomes unstable\nunder high pressure. We have predicted a new phase of VO2 at high pressure that\nhas a monoclinic CaCl2-type structure with metallic nature.\n