Browsing by Subject "phonon"

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    Frictional and vibrational properties of nanostructures
    (2012) Cahangirov, Seymur
    Frictional and vibrational properties of low-dimensional nanostructures have been investigated using the state-of-the-art ab-initio calculations. Stringent test of stability based on calculation of phonon dispersions have been performed for various materials having important potential applications in nanoscience and nanotechnology. Silicene, a counterpart of graphene composed of silicon atoms, is one of such materials with its suitability to well established silicon technology together with eccentric electronic structure due to its honeycomb symmetry. Vibrational spectrum of silicene is found to be exempt from imaginary frequencies upon the puckering of atoms in adjacent sublattices while preserving the symmetry necessary for occurrence of massless Dirac Fermions. Analyses of vibrational properties of silicene nanoribbons and carbon atomic chains revealed new interesting physics like fourth acoustical mode and long-ranged interactions due to Friedel oscillations. Basic concepts of friction science like dissipation phenomena, adiabatic and sudden processes together with several simple models of friction have been summarized. A new method for calculation of corrugation potential between layered lubricants under constant loading pressure is introduced. Transition from stickslip to continuous sliding regime is quantified through definition of frictional figure of merit for layered lubricants. Using this measure tungsten oxide is proposed as an oxidation resistant material which can outperform molybdenum disulfide as a superlubricant. It was found that, the corrugation strengths of graphene layers sandwiched between Ni slabs decrease as the number of layers increase.