We studied NbCl5 and ZnMg alloy intercalated graphite compounds using an optical spectroscopy technique. These intercalated metallic graphite samples were quite challenging to obtain optical reflectance spectra since they were not flat and quite thin. By using both a new method and an in situ gold evaporation technique we were able to obtain reliable reflectance spectra of our samples in the fa...

We here identify by ab initio calculations two distinct three-dimensional three-connected (3D3C) chiral framework structures of carbon in and I41/amd symmetry, respectively, which comprise 3-fold and 4-fold helical chains with complementary chirality. The helical carbon chains are connected by an ethene-type planar π-conjugation, and the resulting structures contain a network of sp(2) carbon bo...

We use large scale ab-initio calculations to describe electronic structures of graphene, graphene nanoribbons, and carbon nanotubes periodically perforated with nanopores. We disclose common features of these systems and develop a unified picture that permits us to analytically predict and systematically characterize metal-semiconductor transitions in nanocarbons with superlattices of nanopores...

first principle calculations were performed using density functional theory within the local spin density approximation (lsda) to understand the electronic properties of au(100)+tbt system and compare the results with au(100) and bulk au properties. band structure, the total dos and charge density for these materials are calculated. we found that the homo for au(100)+tbt becomes broader than au...

We report the simulation results for impact of nonlinear Kerr effect on band structures of a ‎two dimensional photonic crystal (2D-PhC) with no defect, a PhC based W1-waveguide ‎‎(W1W), and also Coupled-Cavity Waveguides (CCWs). All PhC structres are assumed to a ‎square lattice of constant a made of GaAs rods of radius r=0.2a, in an air background. The ‎numerical simulation was performed using...

We perform a comprehensive mapping of GeSi nanowire (NW) electronic band characteristics versus the alloy composition and the diameter (up to 3 nm) using hybrid density functional theory (DFT) calculations, the cluster expansion method and Monte Carlo simulations. We reveal that stable alloy GeSi NW configurations across compositions tend to exhibit asymmetric core-shell structures, which enhan...

A comprehensive ab initio analysis of the ultra high temperature ceramics ZrB2 and HfB2 is presented. Density functional theory (DFT) computations were performed for the electronic, mechanical, thermal, and point defect properties of these materials. Lattice constants and elastic constants were determined. Computations of the electronic density of states, band structure, electron localization f...

Using ab initio hybrid density functional theory based calculations, we report here the electronic and geometric structure properties of three different types of single-walled zigzag silicon carbide nanotube simulated by finite clusters with dangling bonds saturated by hydrogen atoms. These three types differ in the spatial arrangements of Si and C atoms. Full geometry and spin optimizations ha...