The quaternary reciprocal system Li,K||F,I,CrO 4 was partitioned into stable simplexes using graph theory. The system consists of five stable tetrahedra separated by four stable triangles. The chemical interaction between components was described based on the material balance written with account for occurring chemical reactions. Phase equilibria in the quasi-ternary system (LiF) 2 -(KI) 2 -Li 2 CrO 4 were studied for the first time; in this system, the temperature and composition of a ternary eutectic were determined. The limited solubility of two liquid phases manifests itself in the concentration region adjacent to the LiF-KI quasibinary system. A three-dimensional model of the phase complex of the system was constructed in temperature-concentration coordinates.Phase diagrams are of great importance not only for studying theoretical issues of materials and alloys science, but also for solving many practical problems in metallurgy and materials engineering [1,2]. Great attention is given to constructing and investigating phase diagrams. Development of scientific fundamentals of producing functional materials is based on efficient methods of representation of phase diagrams of multicomponent systems using informational technologies [3]. A 3D computer model of the phase complex gives an idea of phase regions of a system, and analysis of the model allows one to describe the liquidus surface, identify monovariant equilibrium lines, predict characteristics of invariant points, and calculate the material balance of equilibrium phases at given parameters of the system, typically, temperature and composition.In this work, the quaternary reciprocal system Li,K||F,I,CrO 4 was partitioned into simplexes, and the chemical interaction was described. The stable triangle (LiF) 2 -(KI) 2 -Li 2 CrO 4 was experimentally studied, and a computer model of a phase state was constructed, which enabled one to fully describe phase states and obtain isothermal and polythermal sections. Figure 1 presents the unfolded pattern of the quaternary reciprocal system Li,K||F,I,CrO 4 . The faceting elements of the system are nine binary systems, two ternary systems, and three ternary reciprocal systems.
OBJECT OF INVESTIGATIONThe thermal properties of the individual components are available in the literature [4][5][6]. The binary systems LiF-LiI, KF-KI, LiI-KI, and LiF-KF were described previously [7], and so were the systems (LiF) 2 -Li 2 CrO 4 , (KF) 2 -K 2 CrO 4 , K 2 CrO 4 -(KI) 2 , and LI 2 CrO 4 -K 2 CrO 4 [8][9][10][11][12][13]. Phase equilibria in the binary system (LiI) 2 -Li 2 CrO 4 and the ternary system (LiF) 2 -(LiI) 2 -Li 2 CrO 4 were predicted before [14]. All the binary systems are eutectic.The ternary system (KF) 2 -(KI) 2 -K 2 CrO 4 was characterized in the literature [15], and so were the ternary reciprocal systems Li, K||F,I and Li,K||F,. The stable diagonal LiF-KI contains a concentration region of phase separation of two liquid phases, and the stable triangle (LiF) 2 -(KF) 2 -K 2 CrO 4 includes the points R 524 of wedging o...