Electronic and vibrational properties of TiSe 2 in the charge-density-wave phase from first principles

摘要: We study the charge-density-wave phase in ${\text{TiSe}}_{2}$ by using first-principles density functional theory calculations with harmonic approximation for electron-phonon coupling. consider several local functionals and both experimental theoretical cell parameters. The results obtained are very sensitive to parameters used. However, we show that, if is used, able reproduce not only structural instability of but also effective distortion observed experiments, irrespective If energy profile displacing atoms independent considered too. With semiempirical Grimme B97-D, aimed at describing better van der Waals forces coupling layers, agreement one analysis gives analogous ones cell. present a electronic structure evolution under deformation. In particular, apply unfolding technique order compare calculated bands distorted angle-resolved photoemission spectroscopy (ARPES) data taken low temperature. obtain between ARPES bands, high temperature, investigate effect correlation on electrons localized Ti-$3d$ orbitals LDA + $U$ method. that within this undistorted good ARPES. On other hand, eliminates phonon system. A possible explanation counterintuitive result proposed. Particularly, possibility taking into account dependence parameter atomic positions suggested.