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Equilibrium phase relations of synthetic minerals prepared by annealing metastable iron sulfides, followed by prolonged isothermal storage in the Earth atmosphere, have been studied by X-ray diffraction. The results demonstrate that prolonged storage of synthetic pyrrhotites annealed at different temperatures makes it possible to identify metastable and stable phases of Fe and S compounds.

The thermodynamic properties of ruthenium complex compound Ru(thd)3, (thd is tris(2,2,6,6-tetramethyl-3,5-heptadionate), Ru(C11H19O2)3 have been studied. Temperatures (434.8 ± 2.0, 452.2 ± 1.0, and 461.1 ± 1.0, and 487.8 ± 1 K) and thermodynamic parameters (enthalpy change ΔH = 13.3 ± 2.0, 2.1 ± 0.5, 6.0 ± 2.0, and 3.8 ± 1 kJ mol–1) of three reversible solid-phase transitions and the melting process have been determined by differential scanning calorimetry. The temperature dependence of the saturated vapor pressure in the range 392–488 K has been established by the flow method. The thermodynamic parameters of sublimation (enthalpy change ΔH = 121 ± 1, 103 ± 3, 101 ± 5, and 86 ± 2 kJ mol–1; entropy change ΔS° = 219 ± 3, 176 ± 7, 173 ± 10, 141 ± 4 J mol–1 K–1) for all four crystalline phases have been calculated. CVD diagrams have been calculated by thermodynamic modeling to determine the equilibrium phase composition of the system. The obtained results allow us to give recommendations on finding the optimal conditions for the CVD process and choosing the precursor.

The translation method for predicting and constructing equilibrium phase diagrams of multicomponent systems is developed based on the compatibility of structural elements of partial constituent (n-component) systems and the general (n + 1)-component system with account for the requirements of the Gibbs phase rule. The invariant equilibrium states in the five-component system NaCl–KCl–MgCl2–CaCl2–H2O at 25°C are studied. This multicomponent system features the options of invariant equilibria where one and the same composition of equilibrium solid phases can be in equilibrium with saturated solutions of differing concentrations. Therefore, this invariant equilibrium is to be reflected in the diagram as a geometric (invariant) image that has a dimension (it may be conventionally referred to as a quasi-point) and not by a point. The dimension of this image is determined by the concentration bounds of components in the equilibrium saturated solution.

A mathematical model of the diffusion interaction of a binary system with several phases on the equilibrium phase diagram is presented. The theoretical and calculated dependences of the layer thickness of each phase in the multiphase diffusion zone on the isothermal annealing time and the ratio of the diffusion parameters in the neighboring phases with an unlimited supply of both components were constructed. The phase formation and growth in the diffusion zone during “reactive” diffusion corresponds to the equilibrium state diagram for two components, and the order of their appearance in the diffusion zone depends only on the ratio of the diffusion parameters in the phases themselves and on the duration of the incubation periods. The dependence of phase appearance on the incubation periods, annealing time, and difference in the movement rates of the components across the interface boundaries was obtained. An example of the application of the model for processing the experimental data on phase growth in a two-component three-phase system was given.

This paper presents thermodynamic modeling results for the magnesium reduction of the MgTa2O6, Mg4Ta2O9, and LiTaO3 tantalates. We have calculated the temperature-dependent heat capacity of the tantalates and determined the adiabatic temperature as a function of initial reactant temperature for reduction reactions in the MgTa2O6-5Mg, Mg4Ta2O9-5Mg, 2LiTaO3-5Mg, and 2LiTaO3-6Mg systems and the equilibrium phase composition of these systems.

Phase equilibria of the Na,K,Mg,Ca‖SO4,Cl-H2O system at 50°C in the halite (NaCl) crystallization field were studied using the translation method. Halite, which is an equilibrium phase of the title system at 50°C, was found to be involved in 25 invariant points, 59 monovariant curves, and 43 divariant fields. A fragment of the equilibrium phase diagram of the title system in the halite crystallization field was constructed.

We have studied the phase composition and crystal structure of CoSb x (1.82 ≤ x ≤ 4.16) nanofilms (30 nm) grown by molecular beam epitaxy on oxidized single-crystal silicon substrates at a temperature of 200°C, followed by heat treatment in vacuum at temperatures from 300 to 700°C. The as-grown films were found to be polycrystalline, with no preferential orientation. The effect of Sb content on the phase composition of the films was consistent with equilibrium phase diagram data for bulk Co-Sb materials. Vacuum annealing at temperatures above 450–500°C led to Sb sublimation not only from the crystalline phase but also from the antimonides, thereby increasing the percentages of the CoSb and CoSb2 phases and reducing the amount of CoSb3. The 30-nm-thick CoSb x (1.8 ≤ x ≤ 4.16) films were thermally stable at temperatures of up to 350°C.

A new class of mathematical solutions has been found when studying the kinetics of plasma of heavy inert gases in the framework of development of plasma lasers. Meta-equilibrium phase diagrams have been obtained for quasi-stationary low-temperature Ar, Kr, and Xe plasmas. These diagrams (as well as the Saha formula) establish an unambiguous correspondence between three parameters: the gas density, electron concentration, and electron temperature. It is shown that recombination processes (in particular, dissociative recombination, consideration of which predetermined the unconventional region in the diagrams) play the role of sources in kinetics equations.

Phase equilibria of the Na,K,Mg,Na,K,Mg,Ca//SO4,Cl-H2O system are studied at 50°C via translation in the crystallization range of glaserite (3K2SO4 · Na2SO4). It is found that glaserite as the equilibrium phase of the investigated system at 50°C participates in the formation of 21 invariant points, 21 monovariant curves, and 34 divariant fields. A fragment of the phase equilibria diagram of the investigated system is constructed in the crystallization range of glaserite.

Phase equilibria of the Na,K,Mg,Ca‖SO4,Cl-H2O system at 50°C in the astrakhanite (Na2SO4 · MgSO4 · 4H2O) crystallization region were studied using the translation method. Astrakhanite was found to be involved, as an equilibrium phase of the title system, in 35 divariant fields, 39 monovariant curves, and 22 invariant points. The data gained were used to construct a fragment of a schematic equilibrium phase diagram of the title system in the astrakhanite crystallization region.

The structure of partially stabilized zirconia crystals has been studied by transmission electron microscopy before and after annealing. Structural characterization of Y2O3-doped (2.8 to 4 mol %) zirconia before annealing showed that all of the samples consisted of twin domains whose size was dependent on the stabilizer content. Annealing at 2100°C increased the domain size in the composition range 2.8–3.7 mol % Y2O3 and reduced it at 4 mol % Y2O3. These structural changes allowed us to determine the position of the representative point relative to the phase boundary in the equilibrium phase diagram of the system.

The equilibrium phase diagrams along the AgInSe2-HgIn2Se4 and AgInSe2-HgSe joins of the ternary system Ag2Se-HgSe-In2Se3 have been constructed using X-ray diffraction and differential thermal analysis. Both joins are pseudobinary, with eutectic phase diagrams (type V in Roseboom’s classification). The eutectics are located at ≃30 mol % HgIn2Se4 (melting point of 1000 K) and ≃54 mol % HgSe (993 K), respectively. Both systems have considerable terminal solid-solution ranges.

The universality of an estimate of the minimum size of small particles with equilibrium phase properties is discussed. Liquid drops in the vapor phase and liquid in porous solids are considered. It is found that the sizes of thermodynamically-stable liquid drops and pore sizes are similar when there is stratifying of a fluid on two phases. It is suggested that the minimum sizes of particles with equilibrium phase properties are the same for magnetic materials as well. Examples of experimental data favoring this suggestion are shown.

The possibility of using the assumption of infinite separation efficiency for the prediction of steady-state operating modes in recycle reactive-distillation processes is analyzed. It is shown that whether the steady-state operating modes is feasible can be decided by analyzing the detailed pattern of the equilibrium phase diagram for the reacting mixture.

The technique and results of computational experiment on the contact melting in a two-component system with an intermetallic compound have been considered. The possibility of existence of metastable states in the liquid interlayer has been assumed. The conditions under which the parabolic law of growth of the liquid-interlayer extension is obeyed and the liquid-interlayer concentration field fits the equilibrium phase diagram have been clarified. Results of the simulation and real experiment have been compared.

Equilibrium phase separation of sterically stabilized ferrocolloids are theoretically studied. The model, which is easily generalized to different physicochemical procedures of ferrocolloid stabilization and gives a quantitatively exact description of computer-calculated phase diagrams of the Stockmayer fluid, is developed. The application of this model for describing the phase separation of real ferrocolloids has demonstrated that, in a ferrocolloid, the key role belongs to the presence of fairly large particles whose van der Waals attraction is insufficiently screened by stabilizing layers. Phase separation can proceed exactly owing to the presence of such particles in ferrocolloids and is due to the joint action of van der Waals and magnetodipole forces under the conditions when the intensity of the latter forces is not sufficient for formation of stable chain aggregates hindering phase separation.

The translation method is used to study equilibria in the system Na, K, Mg, Ca∥SO4, Cl-H2O at 25°C in the crystallization regions of MgCl2·6H2O, CaCl2·6H2O, and 2MgCl2·CaCl2·12H2O. The participation of these salts in the formation of the geometrical images of the title system is determined. The relevant fragments of the equilibrium phase diagram are designed.

A process for indium doping of ZnSe single crystals during vapor phase growth is described. The solubility limit of indium in ZnSe is determined as a function of temperature and zinc selenide stoichiometry. The conclusion is drawn that the entire homogeneity range of ZnSe in the equilibrium phase diagram lies at selenium-enriched compositions.

The reasons for the existence of various scenarios for structural transformations in disordered condensed media, such as liquids and amorphous substances, where both smeared transformations and sharp first-order transitions may occur, were analyzed. The ratio between the spatial scale of structural correlations and the size of the smallest possible region occupied by a new phase in the matrix of initial modification is the key parameter determining the scenario for equilibrium phase transformations in liquids. In amorphous substances, the experimentally observed transformations occur far from equilibrium, and the possible size of the region occupied by the new phase corresponds to the minimal nucleus size. For some amorphous solids, quantitative analysis of the transformation width was carried out and the main classes of covalent substances, in which the smeared or sharp transitions occur, were revealed. Specific features of the interparticle interactions determining various transformation scenarios are discussed.

The behavior of crystalline tetraalkylammonium salts at 290–350 K was studied by differential scanning calorimetry. For tetraethyl- and tetrabutylammonium bromides (Et4NBr and Bu4NBr), the experimental heat capacities agreed well with the literature values. For tetrahexyl-, tetraheptyl-, and tetraoctylam-monium bromides (Hex4NBr, Hep4NBr, and Oct4NBr), phase transitions were found between crystal modifications whose characteristic temperatures depended significantly on the size of the cation. Empirical equations for the temperature dependences of the heat capacities of the salts within the ranges of homogeneous equilibrium phases were derived.

Phase equilibria in the Tb-Mn-O system during the removal of oxygen from the TbMn2O5 compound in stages were studied by the static method on a vacuum circulation unit (973–1173 K) with subsequent X-ray analysis of quenched solid phases. The dissociation of TbMn2O5 was found to occur in three stages. The temperature dependences of equilibrium oxygen pressure were determined experimentally for the phase equilibria observed. The standard thermodynamic functions of the dissociation and formation from the elements of TbMn2O5 and TbMnO3 were calculated.

The phase composition has been studied and an equilibrium phase diagram has been designed for the Al2O3-Li2O-R2O5 (R = Ta or Nb) systems in the subsolidus region up to 1000°C and 85 mol % Li2O. New phases with the composition Li1+x Al1−x O2−x , where x = 0–0.67, have been found.

A microscopic model of phase transitions in a lattice of interacting nodes, where each node is a statistical system with a certain internal structure, is proposed. The main parameter of the model is the configuration entropy related to the number of microscopic states in the node. The proposed model provides a consistent description of the first-and second-order phase transitions and reflects their distinctive features on the microscopic level. Equilibrium phase diagrams in the pressure versus temperature coordinates are constructed in the mean field approximation.