Thermodynamics of Molecular Chains with a Local Asymmetric Double-Well Potential

The thermodynamics of one dimensional chains with asymmetric double-well on-site potential is investigated. Pseudo-Schrödinger equation resulting from the transfer integral method is solved numerically and in terms of semiclassical approximation. This allows exact calculation and qualitative interpretation of the partition function, free energy and the specific heat function. The specific heat exhibits a characteristic hump similar to the one observed in the structures with a symmetric double-well potential. In some systems, another extremely narrow and extremely high, peak might be developed indicating an entropy driven phase transformation. Comparison between this highly simplified model and more practical approaches to the phenomena of photoinduced phase transformations is discussed underlying the possibility of manifestation of quantum effects in some (spin-crossover) systems.     

On ionization energy losses of high-energy electron–positron pair in thin targets

The present Letter deals with consideration of high-energy electron–positron pair ionization losses in thin dielectric plate which it traverses after being emitted from substance where it is created. It is shown that in this case the Chudakov effect of reduction of pair energy losses takes place on much larger distance from its creation point than in the case of the pair motion in homogeneous infinite medium. It is demonstrated that due to transition radiation which appears during the pair emission from the substance the ratio of the pair energy losses in two plates situated on different distances from it is noticeably different from the case when the radiation is neglected.     

Optical identification and electronic configuration of tungsten in 4H- and 6H-SiC

Several optically observed deep level defects in SiC are still unidentified and little is published on their behavior. One of the commonly observed deep level defects in semi-insulating SiC is UD-1.     

Rational Synthesis of “Grape-like” Ni2V2O7 Microspheres as High-capacity Anodes for Rechargeable Lithium Batteries

Vanadates have received booming attention recently as promising materials for extensive electrochemical devices such as batteries and electrocatalysis. However, the enormous difficulties of achieving pure-phase transition metal vanadates, especially for nickel-based, hinder their exploitations. Herein, for the first time, by controlling the amount of ethylene glycol (EG) and reaction time, grape-like Ni₂V₂O₇ (or V₂O₅/Ni₂V₂O₇) microspheres were rationally fabricated. It is demonstrated that the EG can chelate both Ni²⁺ and VO₃⁻ to form organometallic precursors. As anode in lithium-ion batteries (LIBs), it could deliver superior reversible capacity of 1050 mAh/g at 0.1 A/g and excellent rate capability of 600 mAh/g at 4 A/g. The facile hydrothermal synthesis broadens the material variety of nickel vanadates and offers new opportunities for their wider applications in electrochemistry.     

Transition states near rank-two saddles: Correlated electron dynamics of helium

The phase space structure in the vicinity of a rank-two saddle is explored both analytically and numerically. In particular, the geometry of electron dynamics in the neighborhood of the rank-two saddle associated with the nonsequentual double ionization of helium is analyzed. As in the rank-one saddle case, codimension-one normally hyperbolic invariant manifolds turn out to control the rates of the correlated electron dynamics within each energy surface. The construction of these manifolds, however, is more involved here and requires the use of pseudo-hyperbolic invariant manifold theory. Two distinct correlated motions occur, the nonsequential double ionization and the nonsequential exchange of electrons. The relative rates of crossing the barrier are related to the Lyapunov exponents. The dynamics associated with the larger of the two Lyapunov exponents predominates.     

Functional inequalities for the two-parameter extension of the infinitely-many-neutral-alleles diffusion

By explicitly identifying the transition density function, we derived the super-Poincaré and super-log-Sobolev inequalities for the two-parameter extension of the infinitely-many-neutral-alleles diffusion, which in particular implies the Gross log-Sobolev inequality.     

A straightforward synthesis of cationic nitrile ligated transition metal complexes with the [B(C6F5)4] anion

Nitrile ligated transition metal complexes bearing polyfluorinated tetra(aryl)borates as counter anions are highly active initiators/mediators for various polymerization reactions. However, the methods for their preparation are still far too inefficient for widespread use in applied research or in industry. Accordingly, an improved synthesis for two of the most promising species in this assemblage of complexes, namely [Cu(C₆H₅CN)₅][B(C₆F₅)₄]₂ and [Zn(CH₃CN)_4/6][B(C₆F₅)₄]₂, has been developed. This route provides easy access to pure products on a gram scale, by the reaction of copper(II)acetate and diethyl zinc with [H(OEt₂)₂][B(C₆F₅)₄]. Additionally, a new route for the synthesis of the oxonium acid as precursor has been developed, allowing a fast preparation of this compound. Elementary analysis and X-ray crystal structures are in accordance with earlier results on the ease of solvent loss and theoretical studies dealing with acetonitrile-exchange reactions.     

Isomorphous Substitution of Iron and Nickel into Analcime Zeolite

Studies on the effects of iron and nickel incorporation into the hydrothermal synthesis of ANA zeolite were carried out. The presented work reveals that pure Fe‐Al analcime is synthesized by using starting composition with a higher iron(III) content than reported in previous publications. Furthermore, the iron(III) and nickel(II) contents play important roles in the framework of the synthesized zeolite. XRD, FT‐IR spectroscopy, diffuse reflectance UV/Vis spectroscopy, nitrogen adsorption and SEM were used to characterize the synthesized zeolites. These investigations showed that loading of iron and nickel ions in ANA zeolite changes the pore size and morphology of analcime zeolite.     

Electrospray Mass Spectrometric Study on Complexation of Transitional Metal Ions with Oligobipyridine Ligand

Positive-ion mode electrospray mass spectrometry (ES-MS) was used to investigate the reaction of oligobipyridine ligand L (L = 5,5'-bis[2-(2,2'-bipyridin-6-yl)ethyl]-2,2'-bipyridine) with M(ClO₄)₂ in various mole ratios [M = Fe(II), Co(II), Ni(II) and Cu(II)]. The results indicate that the oligobipyridine L coordinated to the transitional metal ions to form mononuclear complexes. The ES mass spectra of isolated complex [FeL₃](PF₆)₂ were measured under various electrospray conditions to examine the influence of the spray voltage, capillary temperature, capillary voltage, and tube lens offset on the fragmentation of the complex in electrospray ionization process. The results show that the fragmentation was mainly controlled by the capillary temperature, capillary voltage, and tube lens offset potential for Finnigan MAT LCQ system. The present study confirmed that the ES-MS is a powerful technique for determining the species existing in solution and for investigation of the reaction between oligobipyridine and transitional metal ions.     

Dynamics of the Photoinduced Ionic-to-Neutral Phase Transition in Tetrathiafulvalene- p -chloranil Studied by Femtosecond Time-resolved Reflection Spectroscopy

Changes in reflection spectra were probed to study the dynamics of photoinduced transformation from ionic to neutral phases in tetrathiafulvalene- p -chloranil crystals. The results have revealed the formation of the precursor of metastable N -phase domains, dynamical lattice relaxation of and proliferation during phase transformation.