Atomic and electronic structures, elastic properties, and optical conductivity of bulk Te and Te nanowires: A first-principles study

We present a comparative study of atomic and electronic structures, Young's modulus, and optical conductivity of trigonal bulk tellurium and its nanowires of different diameters using first-principles density-functional theory calculations based on pseudopotentials and a generalized gradient approximation to exchange-correlation energy. Bulk trigonal Te consists of parallel helices of Te stacked on a triangular lattice in a plane perpendicular to the helical axis. In Te nanowires, interhelical distances change by about 1% of their bulk value due to rearrangement of atoms at the surfaces. Due to a decreased overlap between electronic states of neighboring helices, band gap of nanowires increases with reducing diameter, whereas their Young's modulus correspondingly decreases. Optical conductivity of nanowires depends on their diameter and exhibits a marked anisotropy due to quantum confinement of electronic states in the plane perpendicular to their axis.