The properties of electron transport through CNT/trans-PA/CNT system

Abstract Using a tight-binding model and a tranfer-matrix technique, we numerically investigate the effects of the coupling strength, and the length of the molecule on the electronic transmission through a CNT/(single) molecule/CNT system. With trans-polyacetylene (trans-PA) as the molecule sandwiched between two semi-infinite carbon nanotube(CNT), we rely on Landauer formalism as the basis for studying the conductance properties of this system. Our calculations show that the conductance is sensitive to the CNT/molecule coupling and that it exponentially decreases with the increase in the length of the molecule, as expected

The nature of the phonon eigenstates in quasiperiodic chains (the role of Fibonacci lattices)

Using the forced oscillator method (FOM) and the transfer-matrix technique, we numerically investigate the nature of the phonon states and the wave propagation, in the presence of an external force, in the chains composed of Fibonacci lattices of type site, bond and mixing models, as the quasiperiodic systems. Calculating the Lyapunov exponent and the participation ratio, we also study the localization properties of phonon eigenstates in these chains. The focus is on the significant relationship between the transmission spectra and the nature of the phonon states. Our results show that in the presence of the Fibonacci lattices, at low and medium frequencies the spectra of the quasiperiodic systems are not much different from those of the periodic ones and the corresponding phonon eigenstates are extended. However, the numerical results of the calculations of the transmission coefficient T(ω) , the inverse Lyapunov exponent  Γ(ω)-1 and the participation ratio PR(ω) show that at high frequencies, in contrast with similar ones in disordered systems, the phonon eigenstates are delocalized

The calculation of the conductance and electron tunneling characteristic time from metal-molecule contact in a molecular wire

  In this paper, on the basis of tight-binding model and a generalized Green- function method as well as Lanczos algorithm procedure, the effects of the metal-molecule coupling(MMC) strength on the electronic transmission through a metal-single molecule-metal(MMM) system is investigated. Using the Landauer formalism we study some of the significant conductance properties of this system as a molecular wire. Our results show that with the increase of the length of the molecule, the conductance of the molecular wire decreases exponentially. With trans-polyacetylene (trans-PA) as the molecule, we calculate a characteristic time for electron transmission through the MMM system. This time scale measures the delay caused by tunneling through the MMC. Our calculations show that the conductance is sensitive to the MMC strength. The focus is on the significant relationship between this time scale and the strength of the metal-molecule(trans-PA) coupling

Numerical study of electronic density of states and conductance of a molecular wire coupled with an external molecule

  There is a great interest in the electronic properties of conjugated polymers. Numerous works on the electronic and conduction properties of single-chain conjugated polymers have been published. From an electronic conduction point of view, these systems are quasi-one dimensional. The aim of this paper is to try to investigate corresponding properties in conducting polymers in higher of one-dimension. We study the electronic properties of a polyacetylene chain connected to other molecules. The effect of the size of the molecule and the strength of the coupling to the molecular wire is investigated. The results show that with the increase of the strength of the molecular wire/molecule coupling, the band gap of the system decreases and causes high electronic conduction

Band structure of tetragonal BaTiO

The electronic structure, total density of states DOS and electronic density in ferroelectric tetragonal crystal BaTiO3 are studied using WIEN2k package. This employs the full potential-linearized augmented plan wave FP-LAPW method in the framework of the density functional theory DFT with the generalized gradient approximation (GGA). The results show an indirect band gap of 2.30 eV at the Γ point in the Brillouin zone. The calculated band structure and density of states of BaTiO3 agree with the previous experimental and theoretical results, as do the charge distribution and the prediction of the nature of the chemical bonding

Calculation of electronic structure and density of state for BaTiO3

The electronic structure, density of state (DOS) and electronic density of state inparaelectric cubic crystal Ba TiO3 are studied using full potential-linearized augmented plane wave (FP-LAPW) method in the framework of the density functional theory (DFT) with the generalized gradient approximation (GGA) by the WIEN2K package. The results show a direct band gap of 1.8 eV at the point in the Brillouin zone. The calculated band structure and density of state of BaTiO3 are in good agreement with theoretical and experimental results

Electronic conduction of poly(dG)-poly(dC) DNA in SWNT/DNA/SWNT structure

  In this work, using a tight-binding Hamiltonian model, a generalized Greens function method and Löwdins partitioning techniques, some of the significant properties of the conductance of poly(dG)-poly(dC) DNA molecule in SWNT/DNA/SWNT structure are numerically investigated. In Fishbone model, we consider DNA as a planar molecule which contains M cells and 3 further sites (one base pair site and two backbone sites) in each cell sandwiched between two semi-infinite single-walled carbon nanotubes(SWNT) as the nano-electrodes. Relying on Landauer formalism as the basis for investigating the conductance properties of this system, we focus on the studying of the electron transmission and the current-voltage characteristics of DNA in the foregoing structure. In addition, in the presence of the electric potential between DNA molecule ends, our results suggest that the increasing of the value of applied bias give rise to the large enhancement in the conductance of the system. We also find that, as the tube radius increases, the conductance of the system considerably increases