Фазовая диаграмма системы As-P

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As-P (Arsenic-Phosphorus) I. Karakaya and W.T. Thompson At pressures sufficiently high to suppress the sublimation of As and P (over 3500 kPa), the condensed equilibrium phases of the As-P system are a liquid, L, and three solid solutions-(As), (P), and AsP, each exhibiting considerable variation in composition. The assessed diagram was calculated from a thermodynamic model developed to smooth all experimental findings [48Kle, 71Uga, 81Uga]. Data for pure P were taken from [77Bar]. A subregular solution model for the liquid phase and regular solution models for each of three solid phases were used in the computations. The range of stability for the gaseous phase cannot be calculated with certainty. The vapor phase over which As-P melts contains many molecules including mainly As4, P4, AsP, As2P2, As3P, and AsP3 [79Uga]. The necessary data on all species is incomplete at present. Experimental determinations of phase boundaries show considerable scatter. It is likely that the cooling curves reported by [71Uga] are low due to undercooling. The visual observations of the liquidus by [48Kle] were given low priority in this evaluation. Pure As sublimes at 614 C under standard atmospheric pressure. As is reported to melt at 817 C at 3630 kPa pressure [89Gok]. White P is the common form of elemental P. However, red P may be more stable at 25 C and standard atmospheric pressure [77Bar]. Red P sublimes at 417 C under standard atmospheric pressure. Thermodynamic considerations indicate that red P melts at 576 C when sublimation is suppressed at pressures exceeding 3630 kPa. AsP was reported to have considerable solid solubility [48Kle]. The experimental range of stability reported for this phase varies from 25 to 40 at.% P at one extreme to 40 to 50 at.% P at the other. The composition range over which AsP is stable in the assessed diagram was calculated from a simple thermodynamic model. The crystal structure of AsP has not been identified. It is thought to have an orthorhombic structure [48Kle]. 48Kle: W. Klemm and I.V. Falkowski, Z. Anorg. Chem., 256, 343-348 (1948) in German. 71Uga: Ya.A. Ugai, S.N. Murav›eva, E.G. Goncharov, Yu.P. Afinogenov, and L.A. Bityutskaya, Izv. Akad. Nauk SSSR, Neorg. Mater., 7, 1927-1930 (1971) in Russian. 77Bar: I. Barin, O. Knacke, and O. Kubaschewski, Thermochemical Properties of Inorganic Substances, (Supplement), Springer-Verlag, Berlin (1977). 79Uga: Ya.A. Ugai, G.V. Semenova, E. Berendt, and E.G. Goncharov, Russ. J. Phys. Chem., 53, 576-577 (1979). 81Uga: Ya.A. Ugai, G.V. Semenova, and E.G. Goncharov, Russ. J. Inorg. Chem., 26, 1193-1194 (1981). 89Goc: N.A. Gokcen, Bull. Alloy Phase Diagrams, 10(1), 11-22 (1989). Submitted to the APD Program. Complete evaluation contains 2 figures, 1 table, and 10 references. 1