Calculating the chemical potential of components of a binary solution in a plane-parallel pore

The chemical potential of components of a binary solution is calculated using the expansion of the external field potential in a Taylor series. An expansion of the chemical potential in terms of concentration-concentration direct correlation functions of all orders is obtained. For a plane-parallel pore with an exponential near-wall potential, a solution to the obtained differential equation is constructed in the smooth-inhomogeneity approximation.     

Self-diffusion in water

Applicability of the quasicrystal concept of thermal molecular motions in normal and overcooled water has been studied. Special attention is paid to the mechanism of transition from one temporary position of vibrating molecule to another. Detailed analysis of experimental data about the dependence of the half-width of the quasielastic incoherent peak on the square of the wave vector revealed that the quasicrystal concept is applicable to the overcooled and normal states of water below T _* ≈ 310 K. A new mechanism of self-diffusion in water is suggested for the temperature range T < T _* corresponding to a developed net of hydrogen bonds.     

Calculations of the structural parameters of aqueous solutions of propanol by the Monte Carlo method

Aqueous solutions of propanol were systematically studied by the Monte Carlo method over a wide concentration range at 273 K. The radial distribution functions were calculated and analyzed. This allowed us to perform a detailed analysis of changes in the local structure in the propanol-water system as the content of the alcohol in water increased.     

Structural changes in chlorpropamide at high pressure

The crystalline structure of a molecular crystal of chlorpropamide C₁₀H₁₃ClN₂O₃S is studied by X-ray diffraction at high pressures of up to 4.2 GPa at room temperature. Under normal conditions the structure of chlorpropamide has orthorhombic symmetry with the space group P2₁2₁2₁. At high pressures P > 1.2 GPa, a polymorphic phase transition into the monoclinic phase with the space group P2₁ is observed. The baric dependences of the lattice parameters and unit-cell volumes are obtained for both phases of chlorpropamide.     

Deriving integral equations for radial distribution functions of multicomponent mixtures on the basis of scale transformations in the phase space

It is shown that scale transformations of the coordinate part of the phase space for one of the mixture components correspond to virtual variations in the local density for the same component in a thermodynamic system. The investigation results are used to construct different variants of a generating functional with the goal of deriving a system of integral equations for the radial distribution functions of mixtures. An equation of state, which is a modification of the Tate equation, is obtained. Systems of integral equations that imply, in the limit, the Perkus-Yevick equations and systems of equations for hypernetted chains are derived for radial distribution functions. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 111, No. 3, pp. 473–482, June, 1997.     

Changes in the crystalline structure of chlorpropamide at high pressures and temperatures

The crystalline structure of chlorpropamide is studied by the X-ray diffraction method at high pressures up to 4.2 GPa and in the temperature range 300–450 K. At normal pressure and upon heating to its melting point T = 396 K no phase transitions are found in chlorpropamide. When the initial α form of chlorpropamide is recrystallized, the appearance of a polymorphic ε phase is observed. After recrystallization, the high pressure effect causes partial amorphization of chlorpropamide at pressures of P ～ 3 GPa. Baric and temperature coefficients are obtained for the α and ε forms of chlorpropamide.     

Reorganization of the cluster state in a C60/N-Methylpyrrolidone/water solution: Comparative characteristics of dynamic light scattering and small-angle neutron scattering data

Data on dynamic light scattering from cluster solutions of C₆₀ fullerenes in N-methylpyrrolidone (NMP) and its mixture with water are analyzed. Initial C₆₀/NMP solutions kept for two weeks (i.e., fresher than those analyzed previously) are considered, where the effect of cluster-state reorganization after adding water is recorded more reliably. Based on the size-distribution functions of the clusters, obtained from dynamic light scattering data, model curves of small-angle neutron scattering are calculated and compared with the experimental data.     

Powder structure of magnetic nanoparticles with a substituted pyrrole copolymer shells according to small-angle neutron scattering

Powders of magnetic nanoparticles coated by biocompatible block copolymers (substituted pyrroles) are investigated by small-angle neutron scattering. It is found that the structure of the final precipitates depends on the type of stabilizing shell in the initial magnetic fluids. When dodecylbenzene sulfonic acid is used, separate polydisperse particles with a radius of gyration of 3–5 nm and an irregular surface (fractal dimension of 2.24) are observed in the final samples. For systems with lauric acid, additional scattering from a quasicrystalline structure with a characteristic correlation length of about 10 nm can be seen in the experimental spectra. The difference in the organization of the structure of the studied powders is related to a different polymer coating rate on the surface of the magnetic nanoparticles, which depends on the sorption properties of surfactants in the initial magnetic fluids.