Topological Invariants of Vapor–Liquid, Vapor–Liquid–Liquid and Liquid–Liquid Phase Diagrams

The study of topological invariants of phase diagrams allows for the development of a qualitative theory of the processes being researched. Studies of the properties of objects in the same equivalence class may be carried out with the aim of predicting the properties of unexplored objects from this class, or predicting the behavior of a whole system. This paper describes a number of topological invariants in vapor–liquid, vapor–liquid–liquid and liquid–liquid equilibrium diagrams. The properties of some invariants are studied and illustrated. It is shown that the invariant of a diagram with a miscibility gap can be used to distinguish equivalence classes of phase diagrams, and that the balance equation of the singular-point indices, based on the Euler characteristic, may be used to analyze the binodal-surface structure of a quaternary system.

PROBLEMS OF THE QUATERNARY STRATIGRAPHY OF THE SIBERIAN REGION

This special issue of the journal is devoted to modern controversial subjects arising during the research of the Siberian Quaternary system. The initiative to discuss these problems and new factual material that requires rethinking outdated stratigraphic constructions belonged to the section of the Quaternary system of SIBRMSK and was supported by leading experts actively working in the region. It should be noted that this issue does not cover all the unresolved issues on the geology, stratigraphy and paleogeography of the Quaternary period of Siberia.

PHASE EQUILIBRIUM IN THE INAS2SE4 -INAS2SSE3 AND PROPERTIES OF THE FORMED PHASES

The character of the interaction in the InAs2Se4 -InAs2SSe3 system was investigated and its phase diagram was constructed by DTA, XRD, MSA, as well as by measuring the microhardness and determining the density of the alloys. It was found that the InAs2Se4 -InAs2SSe3 section is a quasi-binary section of the In-As-S-Se quaternary system. Solid solutions based on InAs2Se4 at room temperature reach 10 mol % InAs2SSe3, and on the basis of InAs2SSe3 it extends to 15 mol % InAs2Se4. The lattice parameters are calculated from the region of solid solutions based on InAs2Se4 and InAs2SSe3.

Phase relationships in the Fe-rich region of the Ce–Nd–B–Fe quaternary system at 773 K

The Fe-rich corner of the Ce–Nd–B–Fe quaternary system at 773 K has been experimentally investigated by means of X-ray powder diffraction and scanning electron microscopy equipped with energy dispersive X-ray spectroscopy techniques. No quaternary compound was observed in this system. Ce2Fe14B and Nd2Fe14B were found to form the continuous solid solution (Ce,Nd)2Fe14B. Ce-Fe4B4 and NdFe4B4 also form the solid solution (Ce,Nd)-Fe4B4. The isothermal section consists of 8 three-phase regions and 2 four-phase regions.