A. L. Voskov

A universal method for calculating isobaric-isothermal sections of ternary system phase diagrams

A method for calculating and constructing isobaric-isothermal sections of ternary system phase diagrams with the use of convex hulls was developed. The method is based on the projection of the singularities of the lower part of the Gibbs energy convex hull onto the plane of component mole fractions followed by a geometric analysis of the properties of this projection. The method is applicable to a wide range of ternary systems, it can be used to find tie-line coordinates and determine the phase compositions of all the diagram regions. The quality of the suggested algorithm was estimated, and examples of the construction of several phase diagrams are given.

Calculation of phase equilibria and construction of phase diagrams by convex hull method

Recent findings for a new method developed to calculate phase equilibria are reviewed and analyzed. This method is based on the construction of the convex hulls for characteristic functions in heterogeneous systems. The theoretical basis of this method, as well as the possibilities and features of its practical application in scientific research and teaching chemical thermodynamics, is considered. Software packages developed at the Department of Chemistry of Moscow State University are briefly described.

Phase equilibria in water-propanol(−1, −2) systems

The literature data on the thermodynamic properties of and phase equilibria in the water-1-(2-)C3H7OH systems were considered. The nonrandom two-liquids model was used to optimize the data on liquid-vapor equilibria in these systems, estimate model parameters and errors in them, and calculate and construct the corresponding phase diagrams. The results were compared with the data published earlier.

Thermodynamic assessment of the copper-gadolinium system

The literature data on the thermodynamic properties and phase equilibria in the copper-gadolinium system were generalized. A set of thermodynamic model parameters for system phases that best described these data were obtained. The phase diagram of the system over the temperature range 300–2000 K at a pressure of 1 bar was calculated.

Volumetric Properties of Binary and Ternary Solutions in the Water–Urea–Ammonium Sulfamate System

Densities of liquid phases in the water–urea–ammonium sulfamate ternary system and in the binary water–ammonium sulfamate subsystem were investigated in a wide concentration range at 288.15, 298.15 and 323.15 K. A volumetric model of the aqueous ternary solutions was proposed.

Thermodynamic properties of LnBa2Cu3O6 + z (Ln = Gd, Dy, Ho, Yb, and Y) compounds

Thermodynamic properties of superconductors of LnBa2Cu3O6 + z (Ln = Gd, Dy, Ho, Yb, and Y) are determined by means of EMF using fluoro-ion electrolyte in the temperature range of 900–1250 K. Comparative analyses of the experimental data and thermodynamic models is performed for YBa2Cu3O6 + z compound.

The thermodynamic properties of solutions and phase equilibria in the water-2-butanol-sodium chloride system

Fragments of the phase diagram of the H2O-2-C4H9OH-NaCl system were studied experimentally at 298 and 313 K. The thermodynamic properties of sodium chloride in three-component solutions with ionic strengths up to 1.9 mol/kg and alcohol content in the solvent 4.97 and 10 wt % were measured at 298 and 323 K by the electromotive force method with ion-selective electrodes. The eNRTL (electrolyte Non-Random Two-Liquids) model parameters correctly describing the results of electrochemical measurements of the partial properties of NaCl and phase equilibria in the water-2-butanol-sodium chloride ternary system and binary subsystems constituting it were determined. The isothermal sections of the phase diagram of the H2O-2-C4H9OH-NaCl system were calculated using the method of convex hulls implemented in the TernAPI package.

Development of the PhDi software package for the calculation of phase diagrams of binary systems using parameters of state equations and thermodynamic models for solutions

The PhDi software package developed earlier for calculations of phase equilibria by the convex hull method was modified by incorporating two additional modules: “State equations” and “Local composition thermodynamic models.” The possibility of the application of the convex hull method with cubic state equations to construct phase diagrams of binary systems was shown. A new database containing parameters of the corresponding thermodynamic models has been added to the initial version of the PhDi package. The efficiency of the performance of the package in solving the problem of choosing an appropriate state equation to predict conditions of phase equilibria in binary systems was demonstrated.

Calculation of Ln-Ba (Ln = Gd, Pr, Nd, and Sm) phase diagrams

A thermodynamic model of liquid was suggested and Ln-Ba (Ln = Gd, Pr, Nd, and Sm) phase diagrams were calculated on the basis of generalization of literature data on thermodynamic properties and phase equilibria in lanthanide-barium metallic systems. The interaction parameter of Gd1 − x Bax regular melt was estimated on the assumption of a proportionality between the particle-particle interaction energies of liquid lanthanide and liquid barium, on the one hand, and the lanthanide radius, on the other.