Browsing by Subject "Electric conductance"

Now showing 1 - 4 of 4

Open Access
Ab-initio electron transport calculations of carbon based string structures
(American Physical Society, 2004) Tongay, S.; Senger, R. T.; Dag, S.; Çıracı, Salim
The new stable structures of carbon-based strings and their unusual electronic transport properties were discussed. Total energy and electronic structure calculations using first principles pseudopotential plane wave method within density functional theory (DFT) and supercell geometries were also carried out. It was found that carbon chains were suitable for structural and chemical functionalizations because of their flexibility. These carbon chains also form stable ring, helix, grid and network structures. The results show that the double covalent bonding of carbon atoms underlies their unusual chemical, mechanical and transport properties and carbon chains can form stable string structures with impressive physical properties.
Open Access
Atomic and electronic structure of carbon strings
(IOP Publishing Ltd., 2005) Tongay, S.; Dag, S.; Durgun, Engin; Senger, R. T.; Çıracı, Salim
This paper presents an extensive study of various string and tubular structures formed by carbon atomic chains. Our study is based on first-principles pseudopotential plane wave and finite-temperature ab initio molecular dynamics calculations. Infinite- and finite-length carbon chains exhibit unusual mechanical and electronic properties such as large cohesive energy, axial strength, high conductance, and overall structural stability even at high temperatures. They are suitable for structural and chemical functionalizations. Owing to their flexibility and reactivity they can form linear chain, ring, helix, two-dimensional rectangular and honeycomb grids, three-dimensional cubic networks, and tubular structures. Metal-semiconductor heterostructures and various quantum structures, such as multiple quantum wells and double-barrier resonant tunnelling structures, can be formed from the junctions of metallic carbon and semiconducting BN linear chains. Analysis of atomic and electronic structures of these periodic, finite, and doped structures reveals fundamentally and technologically interesting features, such as structural instabilities and chiral currents. The double covalent bonding of carbon atoms depicted through self-consistent charge density analysis underlies the chemical, mechanical, and electronic properties.
Open Access
Large flat plate models in the physical optics method for RCS calculations
(IEEE, 2004-09) Altıntaş, Ayhan; Çelik, Aslıhan
The calculation of Radar Cross Section (RCS) of arbitrarily large perfectly conducting body is presented. The body is modelled as triangular meshes of any size by the help of graphical tools. For the calculation of scattered field, Physical Optics(PO) surface integral is analytically evaluated over each of the triangular meshes. Due to the analytical integration, there is no limitation on the size of the triangles.
Open Access
Spontaneous and persistent currents in mesoscopic Aharonov-Bohm loops: Static properties and coherent dynamic behavior in crossed electric and magnetic fields
(M A I K Nauka - Interperiodica, 2005) Kulik, I. O.
Mesoscopic or macromolecular conducting rings with a fixed number of electrons are shown to support persistent currents due to the Aharonov-Bohm flux, and the "spontaneous" persistent currents without the flux when structural transformation in the ring is blocked by strong coupling to the externally azimuthal-symmetric environment. In the free-standing macromolecular ring, symmetry breaking removes the azimuthal periodicity, which is further restored at the increasing field, however. The dynamics of the Aharonov-Bohm loop in crossed electric and magnetic fields is investigated within the tight-binding approximation; we show that transitions between discrete quantum states occur when static voltage pulses of prescribed duration are applied to the loop. In particular, the three-site ring with one or three electrons is an interesting quantum system that can serve as a qubit (quantum bit of information) and a qugate (quantum logical gate) because in the presence of an externally applied static electric field perpendicular to a magnetic field, the macromolecular ring switches between degenerate ground states mimicking the NOT and Hadamard gates of quantum computers.