Abstract The Redlich-Kister (RK) three-coefficient expansion for gE is investigated geometrically and its global phase diagram is presented. The azeotropy and stability conditions yield surfaces (envelopes) in the three-dimensional azeotropy space and stability space respectively, whose axes represent variables determined from Henry's constants, pure substance vapor pressures and the highest-order RK coefficient. Zeotropy, single, double, triple, and tangent azeotropy (or saddle-point azeotropy), as well as stability, are identified in regions of the azeotropy and stability spaces. The connection between the two spaces is established. Envelopes for gE = 0 and d g E / d x = 0 are also constructed in the azeotropy or stability spaces, to indicate the gE shape. Some results regarding the shape of gE are transferable to hE and vE when these are described independently by three-coefficient Redlich-Kister expansions. The analysis is applied to eleven actual mixtures, whose state is represented in the azeotropy and stability space. Fitting temperature-dependent RK coefficients allows to estimate the continuous path the mixture follows in both spaces at varying temperature, revealing possible intermediate states and the mixture tendency at the extreme temperatures.

中文翻译：

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二元混合物的三系数 Redlich-Kister 展开全局相图的几何研究

摘要 几何研究了gE的Redlich-Kister (RK)三系数展开式，并给出了其整体相图。共沸和稳定条件分别在三维共沸空间和稳定空间中产生表面（包络），其轴代表由亨利常数、纯物质蒸气压和最高阶 RK 系数确定的变量。共沸、单、双、三和切线共沸（或鞍点共沸）以及稳定性在共沸和稳定性空间的区域中确定。两个空间之间建立了联系。gE = 0 和 dg E / dx = 0 的包络线也在共沸或稳定性空间中构建，以表示 gE 形状。当通过三系数 Redlich-Kister 展开独立描述 hE 和 vE 时，一些关于 gE 形状的结果可转移到 hE 和 vE。该分析适用于 11 种实际混合物，其状态在共沸和稳定性空间中表示。拟合与温度相关的 RK 系数允许估计混合物在不同温度下在两个空间中遵循的连续路径，揭示可能的中间状态和极端温度下的混合物趋势。