Vibrational characteristics of the niobium dichalcogenide. Bulk samples and nanofilms

A model of the niobium diselenide crystal lattice has been proposed. This model sufficiently describes the vibrational characteristics of both bulk samples and nanofilms with a thickness beyond one three-layered structural element. Calculation of the local Green functions and mean-squared atom amplitudes have been performed using the Jacobi-matrix method.Phonon density of states features stipulated by acoustic branches and low-frequency low-dispersion optical modes cross-over have been analyzed.