The phase diagram of the RbBr–NaBr system

In this paper, the data from 75 known phase diagrams of MX–M′X systems (X=F,Cl,Br,I;M and M′ are monovalent metals) are processed by an atomic parameter-pattern recognition method (employing the Fisher method). It is pointed out that the solid solution formers and solid solution nonformers are distributed in different regions in a hyperspace spanned by Pauling’s ionic radii and Batsanov’s electronegativities of the constituent elements. On the basis of a criterion found in the paper, the formation of a solid solution of NaBr in RbBr in the RbBr–NaBr system is suggested. The phase diagram of the RbBr–NaBr system is determined by differential thermal analysis. It is suggested that there is a eutectic at 786 K and 55 mol%RbBr in the phase diagram of RbBr–NaBr, with a solubility of NaBr in RbBr of about 8 mol% at the eutectic temperature, and negligible solid solubility on the NaBr side of the diagram.