cfaed Seminar Series

Abstract:
Nanostructures, such as clusters, nanotubes, nanowires, and nanobelts, have been of both fundamental and technological interest during the past two decades due to the interesting electronic and physical properties intrinsically associated with their low dimensionality. As it has been recognized that the properties of nanoscopic structures can greatly differ from those of macroscopic structures. Edge and finite size effects can strongly influence the properties of these nanostructures. Therefore, a basic understanding of the interplay between structural, mechanical, electronic and optical properties as a function of the particle size and the role of the edge states is
needed. The study of such rather complex systems as a function of particle size and structure requires the application of efficient and reliable methods for atomistic quantum mechanical simulations.

The capability of the density-functional theory based “tight binding” (DFTB) method for such investigations will be demonstrated for 2D MoS2 nanostructures. It will be shown how the size, topology and edge structure influence the electronic, mechanical and the optical properties of such systems. Especially, the size dependence of the optical absorption spectra - obtained by timedependent density-functional theory (TD-DFT) based calculations - will be discussed. The quantum confinement behavior of such nanoparticles, as well as the coexistence of metallic like and
semiconducting properties of such particles will be explained.