K. A. Tatarenko

The dynamics of water hexamer isomerization

The dynamics of water hexamer isomerization was analyzed by classic molecular dynamics using TIP4P and TIP5P empirical interaction potentials. Periodic jump transitions between structural isomers occurred as the internal energy of the cluster grew. Structures prevailing over the energy intervals corresponding to the quasi-liquid and quasi-solid cluster phases were determined. The lifetimes of structural isomers were found.

Formation of microcapsules containing titanium dioxide nanoparticles by pulse expansion of a supercritical solution into a background gas

The formation of microcapsules with a core of TiO2 nanoparticles in a shell of polyethylene glycol by pulse expansion (pulse duration of 400 µs) of a supersonic jet of TiO2-suspension in a supercritical solution of polyethylene glycol (PEG 8000) in CO2 into a background gas (He) is studied. It is shown that the size of capsules and the content of TiO2 in them depend on the pressure of the background gas in the inlet chamber in the range from 0.125 to 3 atm. The upper (1.5 atm) and the lower (0.25 atm) limits of the pressure range, in which microcapsules with a relatively high content of titanium dioxide are formed, are determined.

Kinetic description of the expansion of a supersonic pulsed jet to vacuum: II. Mixtures of monoatomic gases

A model for the expansion of a pulsed jet of a mixture of monoatomic gases was advanced on the basis of the Boltzmann kinetic equation. The Grad method was used to solve the Boltzmann equation. The set of moment equations was analyzed by matching asymptotic expansions. The behavior of the velocity slip and temperature difference was analyzed as a function of the conditions in the source and the component-gas concentrations in the mixture. A functional relationship between these quantities and the form of the interaction potential has been established.

Determination of the dispersion constant of the interaction potential of SF6-SF6 and SF6-Ne at low energies from experiments with supersonic pulse jets

A determination method for the parameters of the potentials of interatomic distances based on the expansion model of a supersonic pulse jet in a vacuum was used for the determination of C6 dispersion constants of interactions of SF6-SF6 and SF6-Ne. The measured value is the value of the position of the maximum of the TOF spectrum. It has been shown that the obtained C6 values satisfactorily coincide with the available data.

Kinetic description of the expansion of a supersonic pulsed jet into a vacuum: III. Determination of the parameters of the atomic interaction potential at low temperatures

A new method based on the kinetic description of a supersonic pulsed jet is proposed for the determination of the parameters of the atomic interaction potential. Analytical relationships are established between the peak position of the observed time-of-flight spectrum, on the one hand, and the source conditions and interaction potential parameters, on the other.

Long-range dispersion C6 coefficient for SF6 dimer: Experimental and theoretical study

The long-range dispersion C6 coefficient for the SF6 dimer is experimentally measured using a technique that uses the expansion of a supersonic pulse jet into a vacuum. A dynamic model of the jet enables us to correlate the position of the maximal peak in the time-of-flight spectrum with the initial conditions of the experiment and the parameters of the intermolecular interaction potential. Due to the low temperature of the jet target, the C6 coefficient can be extracted directly from the experimental results. Theoretical calculation of the C6 dispersion coefficient is also performed by using linearly approximated explicitly correlated coupled-cluster singles and doubles (CCSD(F12)) method with the subsequent utilization of the Casimir-Polder formula. Good agreement of experimental and theoretical results confirms the reliability of results.

Aerodynamic acceleration of heavy particles in a supersonic jet of a binary mixture of gases with disparate-mass components

The method of moments for the ellipsoidal distribution function was used for solving the Boltzmann equation describing binary gas mixtures with large mass disparity and highly diluted heavy component. Analysis of the system of moment equations results in a simple analytic expression for the terminal slip velocities of components that depends on the conditions in the source of jet, composition of mixture, and C6 constant of the attractive branch of the interaction potential. The results are in good agreement with experimental data including low pressure conditions when the Miller-Andres correlation is unsatisfactory.

Gas dynamic model of the expansion of a supercritical carbon dioxide pulse jet: A self-similar solution

The unsteady-state isentropic expansion of an initially homogeneous spherical cloud of a van der Waals gas into a vacuum is considered as a dynamic part of the problem of modeling a real gas pulse jet. A self-similar solution of the gas dynamic equations is obtained. The parameters of the pulse jet (density and temperature) that simulate the conditions of a real experiment are calculated.

Microcapsulation during pulsed expansion of TiO2 suspension in polyethylene glycol solution in supercritical CO2 into background gas

Microcapsulation of titanium dioxide nanoparticles in polyethylene glycol PEG 8000 is performed under pulsed expansion of a jet of polymer solution in supercritical carbon dioxide into the background medium of sulfur hexafluoride and carbon dioxide. Either globule-shaped microcapsules or a film consisting of the product of the bulk intermolecular condensation of the coils are deposited on a substrate. The dependence of the quality and composition of the product deposited from the jet on the type of the background gas and its pressure in a range from 0.125 to 3 atm is investigated.

On the aerodynamic acceleration of heavy particles in a supersonic stream of a binary mixture with strongly disparate masses of components

Based on the moment method of solving the Boltzmann equation with an ellipsoidal velocity distribution function, the aerodynamic acceleration of particles of a heavy mixture component in trace amounts in a light carrier gas are considered. The simple analytical dependence of the limiting average velocity of heavy component particles on conditions in the source and the constant C6 of the attraction branch of interaction potential are obtained. This ratio well describes data from different experiments, including those at low pressures in the stream source, at which the currently known correlation ratios are unsatisfactory.