Structural evolution in binary halide systems with cations in the oxidation state +1

We analyze the structural evolution of binary halide systems with a common anion and cations in the oxidation state +1. For eutectic-type liquid-solid diagrams and in diagrams containing incomplete solid solutions or solid solutions with a liquidus minimum, absolute and relative deflections of the experimental liquidus curve from the ideal curve were determined. The major factors are recognized influencing the structural evolution from systems containing solid solutions to eutectic systems with a positive deflection of the experimental liquidus from the ideal curve and then to ideal eutectic systems, as well as from ideal eutectic systems to eutectic systems with a negative deflection of the experimental liquidus from the ideal curve and then to systems containing compounds.     

Phase diagrams of degenerate states in ternary metal and metal chalcogenide systems with solid solutions

Models with a good-fit have been developed for the phase diagrams of ternary systems with intermediate solid phases of variable and fixed compositions, including diagrams with limited or degenerate solid solutions in subsystems.     

Phase behavior of polylactides in solvent–nonsolvent mixtures

Isothermal phase diagrams for the semicrystalline poly-L-lactide (PLLA) and the amorphous poly-DL-lactide (PDLLA) in combination with several solvent–nonsolvent combinations (dioxane/water, dioxane/methanol, chloroform/methanol, and NMP/water) have been determined. The locations of the liquid–liquid miscibility gap, the solid–liquid miscibility gap and the vitrification boundary in the isothermal phase diagrams at 25°C were identified. The liquid–liquid miscibility gap for the systems with PLLA was located in the same composition range as the corresponding systems with PDLLA. For the systems containing PLLA solid–liquid demixing was thermodynamically preferred over liquid–liquid demixing. Attempts were made to correlate the experimental findings with predictions on the basis of the Flory-Huggins theory for ternary solutions using interaction parameters derived from independent experiments. Qualitative agreement was found between the theoretical predictions and the experimentally obtained liquid–liquid miscibility gap. No good agreement was found for the solid–liquid miscibility gap. © 1996 John Wiley & Sons, Inc.     

On the Phase Diagram of LiF-KCI-KBr and KF-NaCI-NaBr Systems

The phase diagrams of LiF-KCl-KBr and KF-NaCl-NaBr systems have been de'er-mined by visual polythermal method with the X-ray diffraction analysis of solid phases.The thermodynamical behaviour of the molten salt solutions of these systems are estimated on the basis of the data of phase diagrams.The thermodynamical behaviour of these recipioral-salt-pair containing systems is explained by the results of the computerized simulation using Monte Carlo method.     

Topology of melting diagrams of ternary reciprocal systems without continuous solid solutions

The topological properties were considered for melting diagrams of ternary reciprocal systems with constant-composition phases or with isomorphic diagrams with limited solid solutions. An algorithm for constructing the diagrams was described, and an example was given for a melting diagram with one binary peritectic compound and two ternary stoichiometric compounds, all melting without decomposition. A problem of enumeration of all the phase diagrams with such a set of compounds was solved.     

Enumeration of melting diagrams of ternary reciprocal systems without continuous solid solutions

The topological properties were considered for melting diagrams of ternary reciprocal systems with constant-composition phases or limited solid solutions. Relations between the topological parameters of the diagrams were found. Algorithms for solving problems of generation of liquidus surface schemes and their enumeration and classification were presented.     

Correlation of the volumes and heat capacities of solutions with their solid-liquid phase diagrams

Liquid systems which have strong non-idealities, as seen from their thermodynamic properties, often show evidence of these interactions in the solid-liquid phase diagrams. This suggests that some of the structures present in the solid state can persist in the solution state, on a time average, up to temperatures much higher than the melting point. Volumes and heat capacities of typical systems were either taken from the literature or measured to illustrate this correlation with the phase diagrams. With mixtures of aprotic solvents which show nearly-ideal simple eutectic phase diagrams, the properties of the solutions are also nearly ideal. Examples of systems investigated which show strong non-idealities are ionic surfactant solutions, alcohol-water mixtures, chloroform-triethylamine mixtures and lithium salts in aprotic solvents.Paper written in the honor of Loren Hepler on the occasion of his retirement.     

Ab initio computation of the low-temperature phase diagrams of the alkali metal iodide-bromides: MBr(x)I1-x (0 </= x </= 1), Where M = Li, Na, K, Rb, or Cs

We have studied the low-temperature phase diagrams of the systems MBr-MI (M = Li, Na, K, Rb, or Cs) via global exploration of the enthalpy landscapes for many different compositions, leading to candidates for solid solution-like and ordered crystalline phases. For all of these candidates the free enthalpies are computed at the ab initio level, and the low-temperature phase diagrams of the five chemical systems are derived. We find not only the expected stable solid solution in the rocksalt structure type but also metastable solid solutions based on the CsCl type for the RbBr-RbI and CsCl-CsI systems. Furthermore, additional metastable structure candidates exhibiting ordered crystalline structures exist for several compositions. In the case of the LiBr-LiI system, the metastable solid solution based on the wurtzite type was generated, and the location of the miscibility gap was predicted.     

Structural Features of Solid Phases and Topology of Phase Diagrams

The paper considers model phase diagrams of binary and ternary systems involving transformations (transitions) of phase equilibria. The relationship between the type of structural solidstate transformation and the type of phase diagram is shown. Topological series of phase diagrams of systems with continuous and limited types of solid solutions are considered, including phase diagrams with polymorphic transitions between intermediate solid phases of variable composition.     

Solid solutions in binary halide systems having a common anion

Deviations of experimental liquidus curves from ideal curves calculated by the Schröder equation are analyzed for halides that form eutectic systems and systems containing solid solutions. Analysis of phase diagrams shows that the key factors for solid solution formation in binary halide systems having a common anion are as follows: component crystal lattices and close values of the effective radii and polarizing powers of the cations.     

Topology of subsolidus sections of phase diagrams of quaternary reciprocal systems without solid solutions

A problem of constructing subsolidus isobaric–isothermal sections of phase diagrams of quaternary reciprocal systems with constant-composition compounds and limited solid solutions was considered. Relations between the topological characteristics of such sections were derived. Their topological classification was proposed. An algorithm for constructing sections using the theory of finite graphs was developed. A problem of enumerating sections for diagrams with a given set of classification characteristics was solved.     

Formation of continuous solid solutions near the minimum point of a phase diagram

A model of structure ordering in alloys of the compositions corresponding to the minimum points of phase diagrams with continuous series of solid solutions was proposed based on calculating the concentration dependence of the energy of mixing and the results of X-ray powder diffraction study of solid solutions in the systems Sb-As, Sb₂Se₃-Bi₂S₃, and Cu-Mn.     

Graphical representation of polynuclear acid-base and complex equilibria

A calculation procedure for diagrams of log C(M) = f(pL) at various values of the ratio of analytical concentrations, C(L)/C(M), in polynuclear binary systems is described. The diagrams are useful in the resolution of analytical problems of practical interest involving acid-base equilibria (such as the preparation of buffer solutions) and complex equilibria. The presence of a solid phase is also considered.     

Solid clathrate solutions

The classification of solid clathrate solutions may be subdivided into three types: interstitial solutions, those with the substitution of one guest by another and those with the substitution of the particles in a host framework is given. All these types of solutions are illustrated by experimental (or computed) state diagrams of binary and ternary systems of guest-host and host-guest1-guest2 kinds, where host components are water, urea, thiourea and hydroquinone.     

Study of the Ternary Systems M(II)(NO3)2–LiNO3–H2O (M(II) 5 Mg, Ca, Sr, Ba) at 25°C

Summary.  The isothermal solubility diagrams of four aqueous systems containing lithium nitrate and nitrates of group IIA metals – magnesium, calcium, strontium, and barium – were studied at 25°C. No double salt formation was observed. The results were compared with similar nitrate and chloride systems. Some trends in the shape of the phase diagrams were observed. Hydration analysis was applied to the solubility branches, rendering information about ionic processes in saturated solutions. Further, the ratio of activity coefficients of the saturating solid phase in ternary and binary solutions (γ/γ₀) was obtained. Received April 13, 2001. Accepted June 15, 2001     

Study of the Ternary Systems M (II)(NO3)2–LiNO3–H2O ( M (II)?5?Mg, Ca, Sr, Ba) at 25°C

 The isothermal solubility diagrams of four aqueous systems containing lithium nitrate and nitrates of group IIA metals – magnesium, calcium, strontium, and barium – were studied at 25°C. No double salt formation was observed. The results were compared with similar nitrate and chloride systems. Some trends in the shape of the phase diagrams were observed. Hydration analysis was applied to the solubility branches, rendering information about ionic processes in saturated solutions. Further, the ratio of activity coefficients of the saturating solid phase in ternary and binary solutions (γ/γ₀) was obtained.     

Compatibility of copolymers of N-vinylcaprolactam and vinyltetrazoles with aqueous systems

Radical polymerization of N-vinylcaprolactam with 5-vinyl- and 2-methyl-5-vinyltetrazole was used to synthesize water-compatible polymeric products whose aqueous solutions have phase diagrams with a lower critical solution temperature. The thermodynamics of the interaction of the copolymers with water and their behavior in aqueous systems were studied.     

Adsorption, electrophysical, and optical studies of the surface of solid solutions and the binary components of the InSb-ZnTe system

Piezoquartz microweighing, surface electroconductivity measurements, and IR and Raman spectroscopies were used to study the mechanism and regularities of the interaction of carbon monoxide, ammonia, and oxygen, gases of different electronic natures encountered in the environment and various technological processes, with the surface of solid solutions and the binary compounds of the InSb-ZnTe system. An analysis of the results with the use of the acid-base and other physicochemical characteristics of the adsorbents and of the electronic properties of the adsorbate molecules showed that the values of adsorption of the gases lie within α = 10⁻⁵−10⁻³ mol/m². It was demonstrated that, at temperatures above 293 K, the adsorption of CO and NH₃ occurs by the donor-acceptor mechanism, whereas oxygen is adsorbed through the ion-radical mechanism, with the predominant participation of coordinatively unsaturated metal atoms and vacancy defects, respectively. It was revealed that the acid-base, adsorption, electrophysical, and optical properties vary similarly with changing composition of the system, a behavior that suggests the same origin of adsorption sites and inherent surface states and makes it possible to predict the adsorption activity of a surface on the basis of its acid-base properties and the properties of the binary compounds and constituent elements. Similarities and distinctions in the behavior of (InSb) _x (ZnTe)_{1 − x} solid solutions and the binary compounds (InSb and ZnTe) were identified. Specific features of solid solutions, as multicomponent systems, are that adsorption on them is energetically more favorable, especially well pronounced in the acid-base characteristic-composition and adsorption characteristic-composition diagrams. Such diagrams made it possible to determine the solid solution most active with respect to ammonia, (InSb)_0.95(ZnTe)_0.05, which was used to make a selective high-sensitivity gas sensor.     

Partition of the composition tetrahedron during construction of subsolidus isobaric-isothermal sections of the phase diagrams of quaternary systems

A problem of constructing subsolidus isobaric-isothermal sections of phase diagrams with constant-composition compounds and limited solid solutions was considered. Relations between the topological characteristics of such sections were derived. Their topological classification was proposed. An algorithm for constructing sections using the theory of finite graphs was developed. A problem of enumerating sections for diagrams with a given set of classification characteristics was solved.     

Thermodynamics of liquid-crystalline solutions of hydroxypropyl cellulose in water and ethanol

Phase diagrams were constructed and comprehensive thermodynamic analysis was performed for hydroxypropyl cellulose-water and hydroxypropyl cellulose-ethanol systems with the use of the static sorption, calorimetry, cloud-point, polarization microscopy, and X-ray diffraction analysis techniques and the measurement of transmitted polarized light intensity. The concentration dependences of the enthalpy, entropy, and Gibbs energy of the formation of liquid-crystalline phases in the systems were determined. It was found that the formation of liquid-crystalline solutions of hydroxypropyl cellulose in water is associated with the energy term of interaction between the components and that in ethanol solutions is due to changes in combinatorial entropy.