Search

In this work, the mode analysis technique of complex networks nonlinear selfoscillatory vortex-based spin-torque nano-oscillattors (STNOs) with nonidentity and nonisochrony is developed. We construct adjacency matrices of different type of networks and calculate the normal modes. After the calculation of normal modes we shift to truncated equations for slowly varying amplitudes and phases in the normal coordinates using generalized quasi-Hamiltonian approach. Finally, we present the phase dynamics based on the Kuramotoapproach and compare different networks to the ability of synchronization.

When a solute molecule is placed in solution, is it acceptable to presume that its electronic structure is essentially the same as that in the gas phase? In this paper, we address this question from a simulation perspective for the case of the sodium dimer cation (Na 2 ) molecule in both liquid Ar and liquid tetrahydrofuran (THF). In previous work, we showed that, when local specific interactions between a solute and solvent are energetically on the order of a hydrogen bond, the solvent can become part of the chemical identity of the solute. Here, using mixed quantum/classical molecular dynamics simulations, we see that, for the Na + ) molecule in both liquid Ar and liquid tetrahydrofuran (THF). In previous work, we showed that, when local specific interactions between a solute and solvent are energetically on the order of a hydrogen bond, the solvent can become part of the chemical identity of the solute. Here, using mixed quantum/classical molecular dynamics simulations, we see that, for the Na 2 + molecule, solute-solvent interactions lead to two stable, chemically distinct coordination states (Na(THF) 4 -Na(THF) 5 ) that are not only stable themselves as gas-phase molecules but that also have a completely new electronic structure with important implications for the excited-state photodissociation of this molecule in the condensed phase. Furthermore, we show through a set of comparative classical simulations that treating the solute's bonding electron explicitly quantum mechanically is necessary to understand both the ground-state dynamics and chemical identity of this simple diatomic molecule; even use of the quantum-derived potential of mean force is insufficient to describe the behavior of the molecule classically. Finally, we calculate the results of a proposed transient hole-burning experiment that could be used to spectroscopically disentangle the presence of the different coordination states.+ and Na(THF) 5 -Na(THF) 5 + ) that are not only stable themselves as gas-phase molecules but that also have a completely new electronic structure with important implications for the excited-state photodissociation of this molecule in the condensed phase. Furthermore, we show through a set of comparative classical simulations that treating the solute's bonding electron explicitly quantum mechanically is necessary to understand both the ground-state dynamics and chemical identity of this simple diatomic molecule; even use of the quantum-derived potential of mean force is insufficient to describe the behavior of the molecule classically. Finally, we calculate the results of a proposed transient hole-burning experiment that could be used to spectroscopically disentangle the presence of the different coordination states.

Protonated intermediates are postulated to be involved in the rate determining step of many sugar reactions. This paper presents a study of protonated sugar species, isolated in the gas phase, using a combination of infrared multiple photon dissociation (IRMPD) spectroscopy, classical ab initio molecular dynamics (AIMD) and quantum mechanical vibrational self-consistent field (VSCF) calculations. It provides a likely identification of the reactive intermediate oxocarbenium ion structure in a d-galactosyl system as well as the saccharide pyrolysis product anhydrogalactose (that suggests oxocarbenium ion stabilization), along with the spectrum of the protonated parent species: methyl d-galactopyranoside-H+. Its vibrational fingerprint indicates intramolecular proton sharing. Classical AIMD simulations for galactosyl oxocarbenium ions, conducted in the temperature range ∼300-350 K (using B3LYP potentials on-the-fly) reveal efficient transitions on the picosecond timescale. Multiple conformers are likely to exist under the experimental conditions and along with static VSCF calculations, they have facilitated the identification of the individual structural motifs of the galactosyl oxocarbenium ion and protonated anhydrogalactose ion conformers that contribute to the observed experimental spectra. These results demonstrate the power of experimental IRMPD spectroscopy combined with dynamics simulations and with computational spectroscopy at the anharmonic level to unravel conformer structures of protonated saccharides, and to provide information on their lifetimes.

The complicated chemical vapour deposition (CVD) is currently the most viable method of producing graphene. Most studies have extensively focused on chemical aspects either through experiments or computational studies. However, gas-phase dynamics in CVD reportedly plays an important role in improving graphene quality. Given that mass transport is the rate-limiting step for graphene deposition in atmospheric-pressure CVD (APCVD), the interfacial phenomena at the gas-solid interface (i.e., the boundary layer) are a crucial controlling factor. Accordingly, only by understanding and controlling the boundary-layer thickness can uniform full-coverage graphene deposition be achieved. In this study, a simplified computational fluid dynamics analysis of APCVD was performed to investigate gas-phase dynamics during deposition. Boundary-layer thickness was also estimated through the development of a customised homogeneous gas model. Interfacial phenomena, particularly the boundary layer and mass transport within it, were studied. The effects of Reynolds number on these factors were explored and compared with experimentally obtained results of the characterised graphene deposit. We then discussed and elucidated the important relation of fluid dynamics to graphene growth through APCVD.

The two-step quench process of surface-directed spinodal decomposition is numerically investigated by coupling the Flory–Huggins–de Gennes equation with the Cahn–Hilliard–Cook equation. The phase dynamics and formation mechanisms of the wetting layer in two-step surface-directed spinodal decomposition have been concerned in detail. The results demonstrate that a parallel strip structure forms near the wetting layer and propagates into the bulk, when the first quench depth is very shallow and the bulk does not undergo phase separation, and the second quench depths are various points with deeper quench depths. In this case, the wetting layer turns to be unchangeable at the intermediate and later stages of the second quench process, compared to the growth with a time exponent 1/2 during the first quench process. When the first quench depth is deeper and phase separation occurs in the bulk during the first quench process, it is found that a deeper second quench depth can stimulate a more obvious secondary domain structure, and the formation mechanism of the wetting layer changes from logarithmic growth law to Lifshitz–Slyozov growth law. [ABSTRACT FROM AUTHOR]

We investigate the quantum-phase dynamics of a dissipative molecular system interacting with a single-mode amplitude-squeezed field (with a sub-Poissonian photon-number distribution) using the Monte Carlo wave-function method. As quantum dissipation, we consider molecular coherent (phase) and population relaxations, which are caused by nuclear vibration, and cavity relaxation (the dissipation of an internal single mode to outer mode). In this study, we elucidate the effects of these dissipations on the unique quantum dynamical behaviors of this coupled system, e.g., collapse-revival behavior of Rabi oscillations, using the quasiprobability (Q function) distribution of a single-mode field and the off-diagonal molecular density matrix. It is found that although the amplitude-squeezed field exhibits a distinct revival with larger amplitudes of molecular population in the presence of the molecular phase and population relaxations as compared to the coherent field, a very slight cavity relaxation suppresses the revival of molecular population and the increase in the magnitude of off-diagonal molecular density matrices during the quiescent region in the amplitude-squeezed field case more significantly than in the coherent field case. These features are shown to be closely related to the difference in the dynamics of Q function distributions between amplitude-squeezed and coherent fields. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]