Arkadiy M. Kolker

Bio: Arkadiy M. Kolker is an academic researcher from Russian Academy of Sciences. The author has contributed to research in topics: Mole fraction & Solvation. The author has an hindex of 14, co-authored 84 publications receiving 684 citations.

Densities and Volumetric Properties of Ethylene Glycol + Dimethylsulfoxide Mixtures at Temperatures of (278.15 to 323.15) K and Pressures of (0.1 to 100) MPa

Abstract: Densities, ρ, and compressibility coefficients, k = (vo − v)/vo, of ethylene glycol (1) + dimethylsulfoxide (2) mixtures were measured over the whole concentration range at pressures of (0.1 to 100) MPa and temperatures of (278.15 to 323.15) K. Excess molar volumes, isothermal compressibility, and thermal isobaric expansivity coefficients as well as thermal pressure coefficients were calculated. It was revealed that concentration dependences of specific volumes, v, at some state parameters passed a minimum. The shift of minimum position to molar fraction x2 = 0.5 was observed with increasing pressure and decreasing temperature. The negative excess molar volumes, VmE, indicated a compression of EG (1) + DMSO (2) systems when mixing. Composition dependences of isothermal compressibility, κT, and thermal isobaric expansivity coefficients, α, as well as thermal pressure coefficients, β, were near-linear. Both increasing and decreasing of κT and β values were observed with x2 increase depending on temperature ...

Volumetric properties of the water-ethylene glycol mixtures in the temperature range 278–333.15 K at atmospheric pressure

Abstract: Density of the water-ethylene glycol binary mixtures was measured in the entire range of compositions in the temperature range 278–333.15 K (6 values) at atmospheric pressure using a vibration densimeter. Mixtures with low concentrations of ethylene glycol were studied at 15 temperatures in the range of 274–333.15 K. Excess molar volumes VmE, the partial molar volumes of water -V1 and ethylene glycol, -V2, the coefficients of thermal volume expansion α of the mixture, the partial molar volume coefficients of thermal expansion of water \( \bar V_1 \) and ethylene \( \bar V_2 \) were calculated. Excess molar volumes were described using the Redlich-Kister equation. The density ρ of the mixture was found to increase with the increasing ethylene glycol concentration at all temperatures, but at low content of ethylene glycol the dependence ρ = f(T) of the mixture at ∼276.5 K passed through a maximum. The coefficient α increases sharply in the composition range 0 277 K is positive for all compositions. The dependences \( \bar \alpha _1 \) = f (x) and \( \bar \alpha _2 \) = f (x) are complex in whole temperature range and are characterized by the presence of an extremum. VmE values are negative at all temperatures, and upon increase in the temperature the deviation from ideality decreases (x is the mole fraction of ethylene glycol).

Thermal behavior and electrochemistry of protic ionic liquids based on triethylamine with different acids

Abstract: Protic ionic liquids (PILs) composed of the triethylammonium cation with dihydrogen phosphite, tosylate, and trifluoroacetate anions were synthesized. All samples were salts with melting points below 100 °C and were characterized via NMR spectroscopy, attenuated total reflection (ATR) spectroscopy, differential scanning calorimetry (DSC), and thermogravimetry (TG). The electrochemical characteristics of each protic ionic liquid were obtained using a combination of impedance spectroscopy and cyclic voltammetry. Moreover, the influence of water on the thermal behavior and conductivity of triethylammonium tosylate is studied. A linear correlation between the temperatures of melting and crystallization is established for a number of PILs, including both derivatives of triethylamine with different acids reported in the literature and the newly synthesized PILs. The optimal combination of thermal characteristics and electroconductivity was observed for triethylammonium trifluoroacetate and tosylate.

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Abstract: : The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

A temperature predictor for parallel tempering simulations

Abstract: An algorithm is proposed that generates a set of temperatures for use in parallel tempering simulations (also known as temperature-replica exchange molecular dynamics simulations) of proteins to obtain a desired exchange probability Pdes. The input consists of the number of protein atoms and water molecules in the system, information about the use of constraints and virtual sites and the lower temperature limits. The temperatures generated yield probabilities which are very close to Pdes (correlation 97%), independent of force field and over a wide temperature range. To facilitate its use, the algorithm has been implemented as a web server at http://folding.bmc.uu.se/remd.

Molecular Dynamics Study of Hydration in Ethanol−Water Mixtures Using a Polarizable Force Field†

Abstract: The abnormal physicochemical characteristics of ethanol solvation in water are commonly attributed to the phenomenon of hydrophobic hydration. To investigate the structural organization of hydrophobic hydration in water−ethanol mixtures, we use molecular dynamics simulations based on detailed atomic models. Induced polarization is incorporated into the potential function on the basis of the classical Drude oscillator model. Water−ethanol mixtures are simulated at 11 ethanol molar fractions, from 0.05 to 0.9. Although the water and ethanol models are parametrized separately to reproduce the vaporization enthalpy, static dielectric constant, and self-diffusion constant of neat liquids at ambient conditions, they also reproduce the energetic and dynamical properties of the mixtures accurately. Furthermore, the calculated dielectric constant for the various water−alcohol mixtures is in excellent agreement with experimental data. The simulations provide a detailed structural characterization of the mixtures. A...

Polarizable Force Fields for Biomolecular Simulations: Recent Advances and Applications.

Abstract: Realistic modeling of biomolecular systems requires an accurate treatment of electrostatics, including electronic polarization. Due to recent advances in physical models, simulation algorithms, and computing hardware, biomolecular simulations with advanced force fields at biologically relevant timescales are becoming increasingly promising. These advancements have not only led to new biophysical insights but also afforded opportunities to advance our understanding of fundamental intermolecular forces. This article describes the recent advances and applications, as well as future directions, of polarizable force fields in biomolecular simulations.

Standard partial molar volumes of electrolytes and ions in nonaqueous solvents.

Abstract: To date, much has been achieved in the determination of the molar volumes of electrolytes and ions in nonaqueous solvents. This review compiles and critically assesses the data available in the open literature for the standard partial molar volumes of electrolytes, V°, and their ionic constituents, V°(ion), in nonaqueous solvents at 298.15 K. Focus is on electrolytes composed of simple (monatomic and asymmetrical polatomic) ions, and salts containing ions such as triflate and acetate.