• A
  • A
  • A
  • ABC
  • ABC
  • ABC
  • А
  • А
  • А
  • А
  • А
Regular version of the site
Of all publications in the section: 29
Sort:
by name
by year
Article
L.A. Surin. Journal of Chemical Physics. 2018. Vol. 148. No. 4. P. 04413-1-04413-11.

Ab initio calculations of the intermolecular potential energy surface (PES) of CO-N-2 have been carried out using the closed-shell single-and double-excitation coupled cluster approach with a non-iterative perturbative treatment of triple excitations method and the augmented correlation-consistent quadruple-zeta (aug-cc-pVQZ) basis set supplemented with midbond functions. The global minimum (D-e = 117.35 cm(-1)) of the four-dimensional PES corresponds to an approximately T-shaped structure with the N-2 subunit forming the leg and CO the top. The bound rovibrational levels of the CO-N-2 complex were calculated for total angular momenta J = 0-8 on this intermolecular potential surface. The calculated dissociation energies D-0 are 75.60 and 76.79 cm(-1) for the ortho-N-2 (A-symmetry) and para-N-2 (B-symmetry) nuclear spin modifications of CO-N-2, respectively. Guided by these bound state calculations, a new millimeter-wave survey for the CO-N-2 complex in the frequency range of 110-145 GHz was performed using the intracavity OROTRON jet spectrometer. Transitions not previously observed were detected and assigned to the subbands connecting the K = 0 and 1, (j(CO), j(N2)) = (1, 0) states with a new K = 1, (j(CO), j(N2)) = (2, 0) state. Finally, the measured rotational energy levels of the CO-N-2 complex were compared to the theoretical bound state results, thus providing a critical test of the quality of the PES presented. The computed rovibrational wave functions were analyzed to characterize the nature of the different bound states observed for the two nuclear spin species of CO-N2.

Added: Nov 15, 2018
Article
Leonid A. Surin. Journal of Chemical Physics. 2020. Vol. 152. P. 234304-1-234304-12.

We present a five-dimensional intermolecular potential energy surface (PES) of the NH3–N2 complex, bound state calculations, and new microwave (MW) measurements that provide information on the structure of this complex and a critical test of the potential. Ab initio calculations were carried out using the explicitly correlated coupled cluster [CCSD(T)-F12a] approach with the augmented correlation-consistent aug-cc-pVTZ basis set. The global minimum of the PES corresponds to a configuration in which the angle between the NH3 symmetry axis and the intermolecular axis is 58.7○ with the N atom of the NH3 unit closest to the N2 unit, which is nearly parallel to the NH3 symmetry axis. The intermolecular distance is 7.01 a0, and the binding energy De is 250.6 cm–1. The bound rovibrational levels of the four nuclear spin isomers of the complex, which are formed when ortho/para (o/p)-NH3 combines with (o/p)-N2, were calculated on this intermolecular potential surface. The computed dissociation energies D0 are 144.91 cm−1, 146.50 cm−1, 152.29 cm−1, and 154.64 cm−1 for (o)-NH3–(o)-N2, (o)-NH3–(p)-N2, (p)-NH3–(o)-N2, and (p)-NH3–(p)-N2, respectively. Guided by these calculations, the pure rotational transitions of the NH3–N2 van der Waals complex were observed in the frequency range of 13–27 GHz using the chirped-pulse Fourier-transform MW technique. A complicated hyperfine structure due to three quadrupole 14N nuclei was partly resolved and examined for all four nuclear spin isomers of the complex. Newly obtained data definitively established the K values (the projection of the angular momentum J on the intermolecular axis) for the lowest states of the different NH3–N2 nuclear spin isomers.

Added: Nov 12, 2020
Article
Kolesnikov A., Budkov Y., Gor G. Y. Journal of Chemical Physics. 2020. Vol. 153. P. 194703-194712.

Mesoporous materials play an important role both in engineering applications and in fundamental research of confined fluids. Adsorption goes hand in hand with the deformation of the absorbent, which has positive and negative sides. It can cause sample aging or can be used in sensing technology. Here, we report the theoretical study of adsorption-induced deformation of the model mesoporous material with ordered corrugated cylindrical pores. Using the classical density functional theory in the local density approximation, we compared the solvation pressure in corrugated and cylindrical pores for nitrogen at sub- and super-critical temperatures. Our results demonstrate qualitative differences between solvation pressures in the two geometries at sub-critical temperatures. The deviations are attributed to the formation of liquid bridges in corrugated pores. However, at super-critical temperatures, there is no abrupt bridge formation and corrugation does not qualitatively change solvation pressure isotherms. We believe that these results could help in the analysis of an adsorption-induced deformation of the materials with distorted pores.

Added: Nov 18, 2020
Article
B.V. Andryushechkin, V.M. Shevlyuga (Шевлюга В. М., T.V.Pavlova et al. Journal of Chemical Physics. 2018. Vol. 148. No. 24. P. 244702-1-244702-6.

The adsorption of O2 on Ag(111) between 300 and 500 K has been studied with temperature-programmed desorption (TPD) and scanning tunneling microscopy (STM). At the first stage of adsorption, the disordered local oxide phase (commonly looking in STM as an array of black spots) is formed on the surface irrespective of the substrate temperature. The maximum concentration of black spots was found to be ≈0.11 ML, which corresponds to an oxygen coverage of ≈0.66 ML. Taking into account that the nucleation of the Ag(111)-p(4 × 4)-O phase starts after the saturation of the disordered phase, one can conclude that its coverage is at least not less than 0.66 ML. The analysis of STM and TPD data shows that the thermodesorption peak (m/e = 32) at 570 K is related exclusively to the decomposition of the p(4 × 4) phase, while the local oxide phase does not contribute to desorption.

Added: Jan 10, 2019
Article
Budkov Y., Kolesnikov A., Georgi N. et al. Journal of Chemical Physics. 2015. Vol. 142. No. 17. P. 174901-1-174901-10.

We develop a first-principle equation of state of salt-free polyelectrolyte solution in the limit of infinitely long flexible polymer chains in the framework of a field-theoretical formalism beyond the linear Debye-Hueckel theory and predict a liquid-liquid phase separation induced by a strong correlation attraction. As a reference system, we choose a set of two subsystems—charged macromolecules immersed in a structureless oppositely charged background created by counterions (polymer one component plasma) and counterions immersed in oppositely charged background created by polymer chains (hard-core one component plasma). We calculate the excess free energy of polymer one component plasma in the framework of modified random phase approximation, whereas a contribution of charge densities’ fluctuations of neutralizing backgrounds we evaluate at the level of Gaussian approximation. We show that our theory is in a very good agreement with the results of Monte Carlo andMDsimulations for critical parameters of liquid-liquid phase separation and osmotic pressure in a wide range of monomer concentration above the critical point, respectively.

Added: May 2, 2015
Article
Budkov Yu.A., Kolesnikov A., Georgi N. et al. Journal of Chemical Physics. 2014. Vol. 141. P. 014902-1-014902-9.

We present a statistical model of a dilute polymer solution in good solvent in the presence of lowmolecular weight cosolvent. We investigate the conformational changes of the polymer induced by a change of the cosolvent concentration and the type of interaction between the cosolvent and the polymer. We describe the polymer in solution by the Edwards model, where the partition function of the polymer chain with a fixed radius of gyration is described in the framework of the mean-field approximation. The contributions of polymer-cosolvent and the cosolvent-cosolvent interactions in the total free energy are treated also within the mean-field approximation. For convenience we separate the system volume on two parts: the volume occupied by the polymer chain expressed through its gyration volume and the bulk solution. Considering the equilibrium between the two subvolumes we obtain the total free energy of the solution as a function of radius of gyration and the cosolvent concentration within gyration volume. After minimization of the total free energy with respect to its arguments we obtain a system of coupled equations with respect to the radius of gyration of the polymer chain and the cosolvent concentration within the gyration volume. Varying the interaction strength between polymer and cosolvent we show that the polymer collapse occurs in two cases— either when the interaction between polymer and cosolvent is repulsive or when the interaction is attractive. The reported effects could be relevant for different disciplines where conformational transitions of macromolecules in the presence of a cosolvent are of interest, in particular in biology, chemistry, and material science.

Added: Mar 19, 2015
Article
Tyutnev A. P., Novikov S. Journal of Chemical Physics. 2013. Vol. 138. No. 104120. P. 1-9.

We present the results of Monte Carlo simulations of the charge carrier transport in a disordered molecular system containing spatial and energetic disorders using the dipolar glass model. Model parameters of the material were chosen to fit a typical polar organic photoconductor polycarbonate doped with 30% of aromatic hydrazone, whose transport properties are well documented in literature. Simulated carrier mobility demonstrates a usual Poole-Frenkel field dependence and its slope is very close to the experimental value without using any adjustable parameter. At room temperature transients are universal with respect to the electric field and transport layer hickness. At the same time, carrier mobility does not depend on the layer thickness and transients develop a well-defined plateau where the current does not depend on time, thus demonstrating a non-dispersive transport regime. Tails of the transients decay as power law with the exponent close to −2. This particular feature indicates that transients are close to the boundary between dispersive and non-dispersive transport regimes. Shapes of the simulated transients are in very good agreement with the experimental ones. In summary, we provide a first verification of a self-consistency of the dipolar glass transport model, where major transport parameters, extracted from the experimental transport data, are then used in the transport simulation, and the resulting mobility field dependence and transients are in very good agreement with the initial experimental data. © 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4794791]

Added: Apr 3, 2013
Article
Budkov Y., Kolesnikov A., Kiselev M. Journal of Chemical Physics. 2015. Vol. 143. P. 201102-1-201102-4.

We study the conformational behavior of polarizable polymer chain under an external homogeneous electric field within the Flory type self-consistent field theory. We consider the influence of electric field on the polymer coil as well as on the polymer globule. We show that when the polymer chain conformation is a coil, application of external electric field leads to its additional swelling. However, when the polymer conformation is a globule, a sufficiently strong field can induce a globule-coil transition.We show that such “field-induced” globule-coil transition at the sufficiently small monomer polarizabilities goes quite smoothly. On the contrary, when the monomer polarizability exceeds a certain threshold value, the globule-coil transition occurs as a dramatic expansion in the regime of first-order phase transition. The developed theoretical model can be applied to predicting polymer globule density change under external electric field in order to provide more efficient processes of polymer functionalization, such as sorption, dyeing, and chemical modification

Added: Nov 25, 2015
Article
A.P. Tyutnev, S.V. Novikov, V.S. Saenko et al. Journal of Chemical Physics. 2017. Vol. 147. No. 11. P. 114901-1-114901-8.

We have performed Monte-Carlo simulations of the charge carrier transport in a model molecularly doped polymer using three most popular hopping theories (the dipolar glass model, the Gaussian disorder model, and an intermediate between them) in a wide range of applied electric fields and temperatures. Time of flight transients have been computed and analyzed in logarithmic coordinates to study the Poole-Frenkel field dependence, the non-Arrhenius mobility temperature dependence, and the nondispersive versus dispersive current shapes. We also have made an attempt to estimate the total disorder energy directly from simulation data at the lowest electric field thus checking the consistency of the model fitting. Computational results have been compared with the analytical and experimental information available in the literature.

Added: Sep 15, 2017
Article
Kondratyuk N. Journal of Chemical Physics. 2019. Vol. 151. No. 7. P. 074502-1-074502-8.

Decades of molecular simulation history proved that the Green-Kubo method for shear viscosity converges without any problems in atomic and simple molecular liquids, unlike liquids with high values of viscosity. In the case of highly viscous liquids, the time decomposition method was developed in 2015 by Maginn and co-authors [Y. Zhang, A. Otani, and E. J. Maginn, J. Chem. Theory Comput. 11, 3537–3546 (2015)] which allows us to improve the convergence of the Green-Kubo integral. In this paper, the contributions of intramolecular and intermolecular force field parts to the viscosity integral are discovered to gain the understanding of the Green-Kubo method. The n-alkanes from n-ethane to n-pentane at 330 K in the optimized potentials for liquid simulations-all atom force field are used as reference models. The dependencies of these contributions and decay times of the corresponding correlation functions on the chain length are observed. The nonequilibrium simulations are carried out to verify the Green-Kubo results. The obtained values of viscosity are compared with experimental data.

Added: Oct 22, 2019
Article
Boulatov A., Burin A. L. Journal of Chemical Physics. 2020. Vol. 153. No. 13. P. 134102.

The low temperature transport of electron, or vibrational or electronic exciton towards polymer chains turns out to be dramatically sensitive to its interaction with transverse acoustic vibrations. We show that this interaction leads to substantial polaron effect and decoherence, which are generally stronger than those associated with longitudinal vibrations. For site-dependent interactions transverse phonons form subohmic bath leading to the quantum phase transition accompanied by full suppression of the transport at zero temperature and fast decoherence characterized by temperature dependent rate k2 ∝ T3/4 at low temperature while k2 ∝ T2 for site-independent interactions. The latter dependence was used to interpret recent measurements of temperature dependent vibrational energy transport in polyethylene glycol oligomers.  

Added: Oct 14, 2020
Article
Kharazmi A., Priezjev N. Journal of Chemical Physics. 2015. Vol. 142. P. 234503.

Molecular dynamics simulations are carried out to study the translational and rotational diffusion of a single Janus particle immersed in a dense Lennard-Jones fluid. We consider a spherical particle with two hemispheres of different wettabilities. The analysis of the particle dynamics is based on the time-dependent orientation tensor, particle displacement, as well as the translational and angular velocity autocorrelation functions. It was found that both translational and rotational diffusion coefficients increase with decreasing surface energy at the nonwetting hemisphere, provided that the wettability of the other hemisphere remains unchanged. We also observed that in contrast to homogeneous particles, the nonwetting hemisphere of the Janus particle tends to rotate in the direction of the displacement vector during the rotational relaxation time.

Added: Dec 6, 2017
Article
Novikov S.V. Journal of Chemical Physics. 2018. Vol. 148. No. 2. P. 024505-1-024505-10.

Diffusive transport of a particle in a spatially correlated random energy landscape having exponential density of states has been considered. We exactly calculate the diffusivity in the nondispersive quasi- equilibrium transport regime for the 1D transport model and found that for slow decaying correlation functions the diffusivity becomes singular at some particular temperature higher than the temperature of the transition to the true non-equilibrium dispersive transport regime. It means that the diffusion becomes anomalous and does not follow the usual ∝ t^{1/2} law. In such situation, the fully developed non-equilibrium regime emerges in two stages: first, at some temperature there is the transition from the normal to anomalous diffusion, and then at lower temperature the average velocity for the infinite medium goes to zero, thus indicating the development of the true dispersive regime. Validity of the Einstein relation is discussed for the situation where the diffusivity does exist. We provide also some arguments in favor of conservation of the major features of the new transition scenario in higher dimensions.

Added: Jul 12, 2018
Article
Novikov S. V. Journal of Chemical Physics. 2015. Vol. 143. No. 16. P. 164510-164510-6.

Far tails of the density of state (DOS) are calculated for the simple models of organic amorphous material, the model of dipolar glass and model of quadrupolar glass. It was found that in both models far tails are non-Gaussian. In the dipolar glass model, the DOS is symmetric around zero energy, while for the model of quadrupolar glass, the DOS is generally asymmetric and its asymmetry is directly related to the particular geometry of quadrupoles. Far tails of the DOS are relevant for the quasi-equilibrium transport of the charge carriers at low temperature. Asymmetry of DOS in quadrupolar glasses means a principal inequivalence of the random energy landscape for the transport of electrons and holes. Possible effect of the non-Gaussian shape of the far tails of the DOS on the temperature dependence of carrier drift mobility is discussed.

Added: Nov 20, 2015
Article
Felderhof B., Sokolov V. V., Eminov P. A. Journal of Chemical Physics. 2010. Vol. 132. No. 18. P. 184907- 1-184907-7.

The dynamics of ferrofluids is discussed on the basis of Maxwell’s equations and the balance equations for mass, momentum, angular momentum, and energy. It is shown that the requirement of irreversible thermodynamics that the local rate of entropy production be positive definite allows equations of motion, and a corresponding magnetic relaxation equation, characterized by free convective parameters.

Added: Nov 29, 2012
Article
Felderhof B., Sokolov V. V., Eminov P. A. Journal of Chemical Physics. 2011. Vol. 135. No. 14. P. 144901-1-144901-5.

A Hamiltonian field theory of ferrohydrodynamics is derived, with dissipation included by use of a Rayleigh dissipation function. It is shown that kinematic assumptions on the behavior of magnetization under displacements of a volume element of fluid leave a certain freedom in the construction of dynamical equations describing the time-dependence of mass density, flow velocity, entropy density, magnetization, and spin density. The convective behavior of magnetization may characterized by two dimensionless coefficients.

Added: Nov 29, 2012
Article
S.V. Novikov. Journal of Chemical Physics. 2017. Vol. 146. No. 2. P. 024504-1 -024504-8.

Hopping charge transport in amorphous semiconductors having spatially correlated exponential density of states has been considered. Average carrier velocity is exactly calculated for the quasi-equilibrium (nondispersive) transport regime. We suggest also a heuristic approach for the consideration of the carrier velocity for the non-equilibrium dispersive regime.

Added: Mar 22, 2017
Article
Hu H., Bao L., Priezjev N. et al. Journal of Chemical Physics. 2017. Vol. 146. P. 034701-1-034701-7.

The slip behavior of simple fluids over atomically smooth surfaces was investigated in a wide range of wall-fluid interaction (WFI) energies at low shear rates using non-equilibrium molecular dynamics simulations. The relationship between slip and WFI shows two regimes (the strong-WFI and weak- WFI regimes): as WFI decreases, the slip length increases in the strong-WFI regime and decreases in the weak-WFI regime. The critical value of WFI energy that separates these regimes increases with temperature, but it remains unaffected by the driving force. The mechanism of slip was analyzed by examining the density-weighted average energy barrier (E) encountered by fluid atoms in the first fluid layer (FFL) during their hopping between minima of the surface potential.We demonstrated that the relationship between slip and WFI can be rationalized by considering the effect of the fluid density distribution in the FFL on E as a function of the WFI energy. Moreover, the dependence of the slip length on WFI and temperature is well correlated with the exponential factor exp(E/(kBT)), which also determines the critical value of WFI between the strong-WFI and weak-WFI regimes.

Added: Dec 6, 2017
Article
Kameneva S., Tyurin D., Feldman V. et al. Journal of Chemical Physics. 2016. No. 145. P. 214309.

Spectroscopic characteristics and X-ray induced transformations of the HCN⋯⋯CO2 complex in solid Ar and Kr matrices were studied by FTIR spectroscopy and ab initio calculations at the CCSD(T) level. The complex was prepared by deposition of the HCN/CO2/Ng gas mixtures (Ng = Ar or Kr). The comparison of the experiment and calculations prove formation of a linear, H-bonded NCH⋯⋯OCO complex with a substantial red shift of the C–H stretching band and a blue shift of the H–C–N bending band in respect to the monomer. This result is in contrast with the previous gas-phase observations, where only T-shape complex was found. Irradiation of deposited matrices leads to formation of CN radicals and HNC molecules and subsequent annealing results in appearance of H2CN and trans-HCNH in both matrices plus HKrCN in the case of Kr. In the presence of CO2, the strongest absorption of trans-HCNH radical demonstrates an additional blue-shifted (by 6.4 cm−1) feature, which was assigned to the N-coordinated complex of this radical with CO2 on the basis of comparison with calculations. To our knowledge, it is the first experimentally observed complex of this radical. No evidence was found for HKrCN⋯⋯CO2 complex, which was explained tentatively by steric hindrance.

Added: Nov 20, 2019
Article
Smirnov G., Stegailov V. Journal of Chemical Physics. 2012. Vol. 136. No. 044523. P. 1-5.

Melting and decay of the superheated sI methane structure are studied using molecular dynamics simulation. The melting curve is calculated by the direct coexistence simulations in a wide range of pressures up to 5000 bar for the SPC/E, TIP4P/2005 and TIP4P/Ice water models and the united atom model for methane. We locate the kinetic stability boundary of the superheated metastable sI structure that is found to be surprisingly high comparing with the predictions based on the classical nucleation theory.

Added: Mar 24, 2014
Article
Leonid Surin. Journal of Chemical Physics. 2018. Vol. 149. No. 22. P. 224305-1-224305-6.

The microwave spectrum of the NH3–N2 van der Waals complex has been observed in a supersonic molecular jet expansion via broadband (2-8 GHz) chirped-pulse Fourier-transform microwave spectroscopy. Two pure rotational R(0) transitions (J = 1 - 0) with different hyperfine structure patterns were detected. One transition belongs to the (ortho)-NH3–(ortho)-N2 nuclear spin isomer in the ground K = 0 state reported earlier [G. T. Fraser et al., J. Chem. Phys. 84, 2472 (1986)], while another one is assigned to the (para)-NH3–(para)-N2 spin isomer in the K = 0 state not reported before (K is the projection of the total angular momentum J on the intermolecular axis). The complicated hyperfine structure arising from three quadrupole 14N nuclei of NH3–N2 was resolved for both transitions, and the quadrupole coupling constants associated with theNH3 andN2 subunits were precisely determined for the first time. These constants provided the dynamical information about the angular orientation of ammonia and nitrogen indicating that the average angle between the C3 axis of NH3 and the N2 axis is about 66. The average van derWaals bond lengths are slightly different for (ortho)-NH3–(ortho)-N2 and (para)-NH3–(para)-N2 and amount to 3.678 Å and 3.732 Å, respectively. Similar results for the deuterated isotopologues, ND3–N2, NHD2–N2, and NH2D–N2, and their nuclear spin isomers were also obtained thus confirming and extending the analysis for the parent NH3–N2 complex.

Added: Feb 2, 2019
1 2