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Two recent and fully open source COSMO-SAC models are assessed for the first time on the basis of very large experimental data sets. The model performance of COSMO-SAC 2010 and COSMO-SAC-dsp (2013) is studied for vapor−liquid equilibrium (VLE) and infinite dilution activity coefficient (γ i ∞) predictions, and it is benchmarked with respect to the group contribution models UNIFAC and mod. UNIFAC(DO). For this purpose, binary mixture combinations of 2 295 components are investigated. This leads to 10 897 γ i ∞ and 6 940 VLE mixtures, which correspond to 29 173 γ i ∞ and 139 921 VLE data points. The model performance is analyzed in terms of chemical families. A MATLAB program is provided for the interested reader to study the models in detail. The comprehensive assessment shows that there is a clear improvement from COSMO-SAC 2010 to COSMO-SAC-dsp and from UNIFAC to mod. UNIFAC(DO). The mean absolute deviation of γ i ∞ predictions is reduced from 95% to 86% (COSMO-SAC 2010 to COSMO-SAC-dsp) and from 73% to 58% (UNIFAC to mod. UNIFAC(DO)). A combined mean absolute deviation is introduced to study the temperature, pressure, and vapor mole fraction errors of VLE predictions, and it is reduced from 4.77% to 4.63% (COSMO-SAC 2010 to COSMO-SAC-dsp) and from 4.47% to 3.51% (UNIFAC to mod. UNIFAC(DO)). Detailed error analyses show that the accuracy of COSMO-SAC models mainly depends on chemical family types, but not on the molecular size asymmetry or polarity. The present results may serve as a reference for the reliability of predictions with COSMO-SAC methods and provide direction for future developments.

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The present paper deals with the microstructural parameters calculated from X-ray diffraction data, electrical and optical investigations, and scanning tunneling microscopy (STM) studies on ZnIn 2 S 4 IIIa layer type CdIn 2 S 4-x Se x (1.75 e x e 2.75) quaternary chalcogenides. Microstructural parameters such as dislocation density, root-mean-square strain, stacking fault probability, crystallite size anisotropy, and layer disorder parameters of these compounds have been calculated. The temperature variation of electrical conductivity (25-400 °C) confirmed semiconducting behavior. The band gaps of all these compounds obtained from STM and optical measurements are in the range 1.57-1.77 eV and are comparable to each other irrespective of the technique used.

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