Monte Carlo study of the ising model phase transition in terms of the percolation transition of “physical clusters”

Finite squareL×L Ising lattices with ferromagnetic nearest neighbor interaction are simulated using the Swendsen-Wang cluster algorithm. Both thermal properties (internal energyU, specific heatC, magnetization |M|, susceptibility) and percolation cluster properties relating to the physical clusters, namely the Fortuin-Kasteleyn clusters (percolation probability P , percolation susceptibility _p, cluster size distributionn _l) are evaluated, paying particular attention to finite-size effects. It is shown that thermal properties can be expressed entirely in terms of cluster properties, P being identical to |M| in the thermodynamic limit, while finite-size corrections differ. In contrast, _p differs from even in the thermodynamic limit, since a fluctuation in the size of the percolating net contributes to, but not to _p. NearT _c the cluster size distribution has the scaling properties as hypothesized by earlier phenomenological theories. We also present a generalization of the Swendsen-Wang algorithm allowing one to cross over continuously to the Glauber dynamics.     

A percolation study of RTS noise in deep sub-micron MOSFET by Monte Carlo simulation

Based on percolation theory and random telegraph signal (RTS) noise generation mechanism, a numerical model for RTS in deep submicron metal-oxide-semiconductor field-effect transistor (MOSFET) was presented, with which the dependence of Tc/Te (where Tc=capture time, Te=emission period ) on energy levels and trap depth with respect to the interface of traps can be simulated. Compared with experimental results, the simulated ones showed a good qualitative agreement.     

Dynamic properties of propylene glycol confined in ZSM-5 zeolite matrix—A computer simulation study

We performed all atom computer simulations of molecular dynamics of propylene glycol confined in ZSM-5 zeolite host matrix in order to study the characteristic of dipolar relaxation process in this system and compare it with recently published results for similar molecular systems confined in single walled carbon nanotubes. We focused on the influence of the geometric confinement inside ZSM-5 1D channels and interaction with the host system on the observed change in the character of deviation from exponential relaxation, as well as on thermal activation characteristic of the process.     

Spectroscopic study of polyphenylquinolines—materials with efficient intramolecular charge transfer

The energy structure and nature of intramolecular charge transfer have been determined for a series of synthesized 2,6-polyphenylquinolines (PPQs) containing resorcinol, oxygen, and phenylamine bridging groups between phenylquinoline cycles and possessing an arylene radical in the form of alkylated derivatives of carbazole or indolo[3,2-b]carbazole, as well as arylated derivatives of carbazole with nitro- and fluorine substituents. The analysis was based on data on their absorption spectra, photosensitivity, carrier photogeneration quantum efficiency, and luminescence. It is shown that the PPQ monomeric unit is a composite intramolecular charge-transfer complex (ICTC) between the donor arylene fragment and the acceptor quinoline cycle; the latter, in turn, is an ICTC between the donor bridging group and quinoline ring (when acceptor fluorine or nitro substituents are introduced into the carbazole structure, the complex becomes ternary), and the narrowest band gap (2.3 eV) corresponds to the PPQ having a phenylamine bridging group and a fragment of indolo[3,2-b]carbazole.     

Cellular automata approach to site percolation on ℤ2. A numerical study

We present a cellular automata model as a new approach to Bernoulli site percolation on the square lattice. A new macroscopic quantity is defined and numerically computed at each level step of the automata dynamics. Its limit manifests a critical behavior at a value of the site occupancy probability quite close to those obtained for site percolation on ² with the best-known numerical methods.     

Transport and percolation in disordered systems—A self-consistent time-local approach

A new self-consistent equation for the transport of excitations in disordered systems, which forms the basis for a new class of time-domain coherent potential approximations, is developed. As an example, we calculate the probability of remaining in the original site G₀(t) as well as the second moment of the distribution of excitations r²(t) for a random mixture of donors which satisfy a master equation with short-range transition rates. A percolation-type transition is observed and its characteristics are analyzed both above and below the transition point.Alfred P. Sloan fellow, Camille and Henry Dreyfus teacher-scholar.     

Level structures of 95,97Mo — A comparative study

High-spin states of ^95,97Mo (Z=42, N=53,55) nuclei have been investigated through ⁸²Se(¹⁸O, xn) reaction at Eb=60 MeV. The level scheme in ⁹⁵Mo has been observed upto ≏ 10 MeV in the present experiment. The level structure shows mainly single particle character. In ⁹⁷Mo, the ground state level sequence has been extended to ≏ 4.5 MeV while the previous information had been up to 2.4 MeV. A negative parity band built on 1437 keV (11/2⁻) excited state has been extended to 5.5 MeV. The structure seems to show a coexistence of single particle and collective modes of excitation. Properties of both the nuclei have been compared with shell model calculations using OXBASH.     

Electronic structure of hexagonal quantum—disc clusters

Within the effective-mass approximation,we investigate the electronic structure of hexagonal quantum-disc clusters using the finite element method.With an increasing amount of quantum dots in the cluster,the electronic energy levels quickly expand into mini-bands.each consisting of discrete,unevenly distributed energy levels,The corresponding electronic eigenfunctions are linear combinations of the electron orbits in each quantum dot.The spatial symmetry of the combination is the same as the electronic eigenfunctioin of a single quantum dot.     

Structural evolution study of 1−2 nm gold clusters

We have explored lowest energy minima structures of gold atom clusters both, charged and neutral (Au\hbox{_nⁿ_{n}^{\nu}}νn with n = 20, 28, 34, 38, 55, 75, 101, 146, 147, 192, 212 atoms and ν = 0, ±1). The structures have been obtained from first principles generalized gradient approximation, density functional theory (DFT) calculations based on norm-conserving pseudopotentials and numerical atomic basis sets. We have found two new disordered or defective isomers lower in energy than their ordered counterparts for n = 101, 147. The purpose of this work is to systematically study the difference between the electronic properties of the two lowest ordered and disordered isomers for each size. Our results agree with previous first principle calculations and with some recent experimental results (Au₂₀ and Au₁₀₁). For each case we report total energies, binding energies, ionization potentials, electron affinities, density of states, highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gaps, Housdorff chirality measure index and their simulated image in a high resolution transmission electron microscopy (HRTEM). The calculated properties of the two low lying (ordered and disordered) isomers show clear differences as to be singled out in a suitable experimental setting. An extensive discussion on the evolution with size of the cohesive energy, the ionization potentials, the electron affinities, the HOMO-LUMO gaps and their index of chirality to determine the crossover between them is given.     

A systematic study on matrix models for Chern–Simons-matter theories

We investigate the planar solution of matrix models derived from various Chern–Simons-matter theories compatible with the planar limit. The saddle-point equations for most of such theories can be solved in a systematic way. A relation to Fuchsian systems play an important role in obtaining the planar resolvents. For those theories, the eigenvalue distribution is found to be confined in a bounded region even when the ?t Hooft couplings become large. As a result, the vevs of Wilson loops are bounded in the large ?t Hooft coupling limit. This implies that many of Chern–Simons-matter theories have quite different properties from ABJM theory. If the gauge group is of the form U_(N1)k1×U_(N2)k2$\mathrm{U}{(N_1)}_{k_1}\times \mathrm{U}{(N_2)}_{k_2}$, then the resolvents can be obtained in a more explicit form than in the general cases.     

A theoretical study of ion selectivity of zeolites—application to chabazite

As a contribution towards a better theoretical understanding of zeolite properties, the mechanism of ion migration through zeolite lattices has been studied with special reference to ion selectivity in chabazite. We have started from the Cartesian coordinates obtained by combining experimental data and the values for a model having standard bond lengths and angles. Then we have applied the Del Re method (with appropriate parameters for Si and Al⁻) to determine the net charges of the framework atoms. Then we have computed the potential energy profiles for one or more cations crossing the larger cavity of the chabazite unit cell (ca 200 atoms). The interaction energy contains electrostatic terms associated with point-charge interaction and polarization effects.Two different pictures have been analyzed: a totally idealized one, where ion motion takes place in the fully dehydrated zeolite, and a more realistic one, where the ion is seen as a moving aquo complex. In the latter case, the presence of the solvent has been taken into account by introducing a dielectric constant depending on ion size and channel diameter. Whereas no significant differences between ions having the same formal charges have been found in the dehydrated case, polarization effects being too small to bring about a distinct selectivity, the model taking solvation into account does predict the expected selectivity, and agrees well with available experimental results. Equilibrium sites, the corresponding free energies, and energy barriers between them have been used for the discussion.The value of the two models in attempts to understand elementary physico-chemical processes in zeolites is emphasized, with extensive reference to existing literature.     

A density functional theory study of small bimetallic PdnAl (n=1–8) clusters

The geometries, stabilities, and magnetic properties of Pd_nAl (n=1–8) neutral clusters are studied using density functional theory with generalized gradient approximation. The growth pattern for different sized Pd_nAl (n=1–8) clusters is Al-substituted Pd_n+1 clusters and it keeps the similar framework of the most stable Pd_n+1 clusters except n=6 and 8. Al atoms in the ground state Pd_nAl isomers tend to occupy the most highly coordinated position. The analysis of stabilities shows that doping an Al atom can enhance the stabilities of the host Pd clusters and the magic number characteristic of Pd₄ cluster cannot be changed, the Pd₃Al cluster has a higher stability. Charges are transferred from Al atom to Pd atoms in all Pd_nAl clusters, so the Al atom is the electron donor, and Pd atoms are the electron accepters. Doping an Al atom decreases the average atomic magnetic moments of the host Pd clusters.     

Experimental modeling of percolation of molten iron through polycrystalline olivine matrix at 2.0–5.5 GPa and 1600°C

The present work was aimed to understand the role of light elements for the penetration of Fe melt through the olivine matrix at high P–T parameters. We studied the mechanism of Fe melt percolation through the olivine matrix, whose interstices are filled with carbon and sulfur. The experiments were performed using a ‘split-sphere’ type multi-anvil high pressure apparatus at pressures 2.0 and 5.5?GPa and a temperature of 1600°C. It was demonstrated that the Fe melt penetrated through the olivine matrix at a relatively high rates in the presence of carbon or sulfur in the interstices. The percolation occurs due to fast dissolution of the light elements into Fe melt and filling of these interstices by the melt.     

Lattice thermal conductivity of δ-graphyne — A molecular dynamics study

Thermal conductivity of δ-graphyne was investigated using reverse non-equilibrium molecular dynamics simulations. The dependence of the thermal conductivities with the temperature, acetylenic linkages, and external strain were explained by the phonon density of states. Our simulations revealed that as the temperature increased, the thermal conductivity of graphene first increased and then decreased, whereas that of δ-graphyne monotonically decreased. Owing to the presence of the acetylenic linkages, a significant reduction was found in the thermal conductivity of δ-graphyne, which resulted in a phonon vibration mismatch or weakened coupling. Moreover, the temperature profile changed from mono linear to the ladder the number of acetylenic linkages increased. These results play a guidance role in the design and application of thermoelectrics devices using 2D carbon materials.     

Chemical passivation of unstable FeO — A Mössbauer study

Highly unstable FeO is chemically passivated by incorporating Cr³⁺ ions by solid solution technique and forming Fe_xOCr³⁺ single phase material. XRD, chemical analysis and Mossbauer spectroscopy are used for the characterization of the freshly prepared as well as samples aged in the desiccator for nearly three months. Optimum concentration range — 0.25 to 0.75 mole% — of Cr₂O₃ has been found to be necessary for stabilizing Fe_xOCr³⁺. x is determined by chemical analysis. Mossbauer and XRD studies have confirmed the chemical passivation of unstable FeO.NCL Communication No. 3905     

A theoretical study of N–H ··· π H-bond interaction of pyrrole: from clusters to the liquid

The N–H?···?π H-bond interactions of clusters and liquid formed by pyrrole molecules were investigated by Quantum Mechanics (QM) and classical Molecular Dynamics (MD), respectively. Based on the optimized geometry at the B97-D/aug-cc-pVTZ level of theory including dispersion correction, the nature and the origin of N–H?···?π H-bond interactions were unveiled by atoms in molecules (AIM), natural bond orbital (NBO), and energy decomposition analysis (EDA). Among them, the AIM analysis gives evidence to the presence of N–H?···?π H-bond interactions, the NBO examination reveals that π?→?σ* donor-acceptor orbital interaction is of great importance. EDA study indicates that N–H?···?π interactions are governed by the electrostatic and dispersion term. Meanwhile, MD simulation with OPLS-AA (optimized potentials for liquid simulations all-atom) was applied to study the pure liquid pyrrole at different temperature. The results confirm the existence of the N–H?···?π H-bond in the pure liquid pyrrole, and further characterized the structures of this H-bond which is somewhat different to the clusters.     

A study of multi-beam DICANNE system

I.IntroductionTheprob1cmofsuppressingstrongpointinterferencesourceisavcryimportantthesisinsonardesign.Fortheana1ogsonar,thesolutionofthisprob1emisquitedifficu1t.Untilthedevelopmentofdigitalsonar,thereissomerescarchreportsaboutsuppressingstrongpointin-terferencesource.Theear1ierworkin1969,dedicatcdbyV.C.Anderson,istheconccptofDICANNE(DigitalInterfcrcnceCance1lingAdaptiveNu1lNetworkEquipment)['l.Thisisadoublecompensatormulti-bcamsystcm.Oneisusedtoformintcrfercncebeamandanothcrisusedtofor…     

Energy density functional study of nuclear matrix elements for neutrinoless ββ decay

We present an extensive study of nuclear matrix elements (NME) for the neutrinoless double-beta decay of the nuclei 48Ca, 76Ge, 82Se, 96Zr, 100Mo, 116Cd, 124Sn, 128Te, 130Te, 136Xe, and 150Nd based on state-of-the-art energy density functional methods using the Gogny D1S functional. Beyond-mean-field effects are included within the generating coordinate method with particle number and angular momentum projection for both initial and final ground states. We obtain a rather constant value for the NMEs around 4.7 with the exception of 48Ca and 150Nd, where smaller values are found. We analyze the role of deformation and pairing in the evaluation of the NME and present detailed results for the decay of 150Nd.