Polarizability versus mobility: atomistic force field for ionic liquids

Based on classical molecular dynamics simulations, we discuss the impact of Coulombic interactions on a comprehensive set of properties of room temperature ionic liquids (RTILs) containing 1,3-dimethylimidazolium (MMIM(+)), N-butylpyridinium (BPY(+)), and bis(trifluoromethane sulfonyl)imide (TFSI(-)) ions. Ionic transport is found to be noticeably hindered by the excessive Coulombic energy, originating from the neglect of electronic polarization in the condensed phase of these RTILs. Starting from the models, recently suggested by Lopes and Padua, we show that realistic ionic dynamics can be achieved by the uniform scaling of electrostatic charges on all interaction sites. The original model systematically overestimates density and heat of vaporization of RTILs. Since density linearly depends on charge scaling, it is possible to use it as a convenient beacon to promptly derive a correct scaling factor. Based on the simulations of [BPY][TFSI] and [MMIM][TFSI] over a wide temperature range, we conclude that the suggested technique is feasible to greatly improve quality of the already existing non-polarizable FFs for RTILs.     

Synthesis of 2H-Thiopirano[3,4-c]pyrazol-7-one Derivatives as the First Example a New Heterocyclic System

Russian Journal of General Chemistry - A series of ethyl 4-[(Z)-(4-oxo-2-thioxo-1,3-thiazolidin-5-ylidene)methyl]-1-aryl-1H-pyrazole-3-carboxylates was obtained as a result of the reaction of ethyl...     

Effect of magnetic field on tunneling systems in glasses

The effect of a magnetic field on two-level tunneling systems in dielectric glasses originates from the magnetic-field-induced rotation of nuclear spins and the ensuing rearrangement of ordered regions (clusters) in the glass structure. This process accounts for the observed variation of both the spontaneous-polarization echo amplitude and the dielectric constant in a magnetic field at low temperatures. The proposed theory is compared with experiment.     

Nonlinear electrohydrodynamic phenomena and droplet generation in charged jets of conducting liquid

Phenomena occurring at the tip of a charged conducting jet are analyzed in detail using numerical methods developed for axially symmetric flows. Universal mechanisms (independent of the method for producing the jet) for droplet formation with different ratios of the Laplace and electrical pressures on the lateral surface are identified. An explanatory analysis is given for all of the nonlinear stages of the classical Rayleigh instability of a charged conducting drop, beginning with the formation of a jet at the surface of the drop and culminating in the generation of a developed jet of secondary droplets. Zh. Tekh. Fiz. 69, 1–9 (November 1999)     

Period doubling cascade and deterministic chaos in a laser self-mode-locked by the combination of inertial negative and positive feedbacks

We proposed a simple laser system that demonstrates the nonlinear dynamics typical for the logistic map: period doubling cascade, periodicity windows, intermittency, and deterministic chaos on the time scale of the cavity round trip.     

Ambipolar drift and breakdown of oscillistor effect in strong magnetic fields

The drift mechanism of helical instability suppression (oscillistor) in electron-hole plasma Ge was, for the first time, investigated. It was found that in strong magnetic fields ($\text{γ}{}_{\mathrm{i=e,h}}\text{= μ}{}_{\mathrm{i}}\text{H/c}\text{a}\text{?}\text{1}$) due to anisotropy of mobility (μ_i ≠ μ_i⊥) the ambipolar drift of helical disturbances of density along the electric field occurs even in quasineutral plasma (n = p), provided μ_e ≠ μ_h. To corroborate the drift mechanism of oscillistor effect breakdown in strong fields the experiments were carried out under the conditions of uniaxial crystal deformation oriented towards 〈111〉 (H, E  〈111〉) resulting in the intervalley redistribution of electrons and additional anisotropy of mobility. Variation in the ambipolar drift velocity connected with the deformation influences essentially the conditions of the helical instability breakdown in strong fields.     

Newton's recursion formula for a 2-matrix argument

Newton's recursion formula for solving nonlinear equations of a 1-matrix (vector) argument is generalized to the case of a 2-matrix argument. The Jacobian 4-matrix of the system is introduced. At the k th recursion the computational process reduces to solving the system of linear algebraic equations obtained, whose order is determined by the number of elements of the 2-matrix argument.Translated fromMatematicheskie Metody i Fiziko-Mekhanicheskie Polya, Issue 34, 1991, pp. 99–100.     

Ab initio calculations of anharmonic vibrational spectroscopy for hydrogen fluoride (HF)n (n = 3, 4) and mixed hydrogen fluoride/water (HF)n(H2O)n (n = 1, 2, 4) clusters

Anharmonic vibrational frequencies and intensities are computed for hydrogen fluoride clusters (HF)n, with n = 3, 4 and mixed clusters of hydrogen fluoride with water (HF)n(H2O)n where n = 1, 2. For the (HF)4(H2O)4 complex, the vibrational spectra are calculated at the harmonic level, and anharmonic effects are estimated. Potential energy surfaces for these systems are obtained at the MP2/TZP level of electronic structure theory. Vibrational states are calculated from the potential surface points using the correlation-corrected vibrational self-consistent field method. The method accounts for the anharmonicities and couplings between all vibrational modes and provides fairly accurate anharmonic vibrational spectra that can be directly compared with experimental results without a need for empirical scaling. For (HF)n, good agreement is found with experimental data. This agreement shows that the M?ller-Plesset (MP2) potential surfaces for these systems are reasonably reliable. The accuracy is best for the stiff intramolecular modes, which indicates the validity of MP2 in describing coupling between intramolecular and intermolecular degrees of freedom. For (HF)n(H2O)n experimental results are unavailable. The computed intramolecular frequencies show a strong dependence on cluster size. Intensity features are predicted for future experiments.     

New borides Er0.917Ni4.09B and ErNi7B3 and their crystal structures

New borides have been synthesized and their crystal structures have been determined using X-ray single-crystal methods, namely: Er_0.917Ni_4.09B, own structure type, space group P6/mmm, a=14.8399(3), c=6.9194(3) Å, R_F=0.0545, and ErNi₇B₃, own structure type, space group I4₁/amd, a=7.6577(2), c=15.5798(5) Å, R_F=0.0451. The relationship between these structures and the structure types of CeCo₄B, Y_0.915Ni_4.12B and Sc₄Ni₂₉B₁₀ has been discussed.