Spontaneous polygonization for a multiwalled carbon nanotubes (MWCNTs) without external pressure is understood by the competition between cohesion energy (with lattice mismatching and defect's ...effect) and curvature elastic energy of tubes inside the MWCNTs. Based on a continuum elastic model and perturbation analysis, the crucial conditions for spontaneous polygonization of MWCNT is expressed by fundamental parameters of MWCNTs, which are in reasonable agreement with all relevant experiments and computer simulations reported in literatures. Present approach can be used in further studies of crossectional geometry-dependent electronic properties of MWCNTs and other inorgnic nanotubes.
In the present work, we study theoretically the electron wave's focusing phenomenon in a single-layered graphene pn junction (PNJ) and obtain the electric current density distribution of graphene ...PNJ, which is in good agreement with the qualitative result in previous numerical calculations (Cheianov et al 2007 Science, 315, 1252). In addition, we find that, for a symmetric PNJ, 1/4 of total electric current radiated from the source electrode can be collected by the drain electrode. Furthermore, this ratio reduces to 3/16 in a symmetric graphene npn junction. Our results obtained by the present analytical method provide a general design rule for an electric lens based on negative refractory index systems.
Spontaneous polygonization for a multi-walled carbon nanotubes (MWCNTs) have been observed for about two decades. In present manuscript, this phenomenon is understood by the competition between ...cohesion energy (with lattice mismatching effect) and curvature elastic energy of tubes inside the MWCNTs. Based on a continuum elastic model and perturbation analysis, the crucial conditions for spontaneous polygonization of MWCNT is expressed by fundamental parameters of MWCNTs, which are in reasonable agreement with all relevant experiments and computer simulations reported in literatures. Present approach can be used in further studies of crossectional geometry-dependent properties of MWCNTs.
The stochastic systems without detailed balance are common in various chemical reaction systems, such as metabolic network systems. In studies of these systems, the concept of potential landscape is ...useful. However, what are the sufficient and necessary conditions of the existence of the potential function is still an open problem. Use Hodge decomposition theorem in differential form theory, we focus on the general chemical Langevin equations, which reflect complex chemical reaction systems. We analysis the conditions for the existence of potential landscape of the systems. By mapping the stochastic differential equations to a Hamiltonian mechanical system, we obtain the Fokker-Planck equation of the chemical reaction systems. The obtained Fokker-Planck equation can be used in further studies of other steady properties of complex chemical reaction systems, such as their steady state entropies.
In present work, we theoretically study the electron wave's focusing phenomenon in a single layered graphene pn junction(PNJ) and obtain the electric current density distribution of graphene PNJ, ...which is in good agreement with the qualitative result in previous numerical calculations Science, 315, 1252 (2007). In addition, we find that for symmetric PNJ, 1/4 of total electric current radiated from source electrode can be collected by drain electrode. Furthermore, this ratio reduces to 3/16 in a symmetric graphene npn junction. Our results obtained by present analytical method provide a general design rule for electric lens based on negative refractory index systems.
A strict method is used to calculate the current-voltage characteristics of a
double-stranded DNA. A more reliable model considering the electrostatic
potential drop along an individual DNA molecular ...wire between the contacts is
considered and the corresponding Green's Function is obtained analytically
using Generating Function method, which avoids difficult numerical evaluations.
The obtained results indicate that the electrostatic drop along the wire always
increases the conductor beyond the threshold than without considering it, which
is in agreement with recent experiments. The present method can also be used to
calculate the current-voltage characteristics for other molecular wires of
arbitrary length.
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