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In this work a fundamental equation of state explicit in the Gibbs free energy was established, which was fitted to experimental data (heat capacity, molar volume, expansion coefficient, and compressibility) of solid carbon dioxide. Almost all of the data that the equation was fitted to are represented within the experimental uncertainty given by the authors. However, only very limited data for the thermodynamic properties of solid carbon dioxide are available. The new equation behaves physically reasonably within its range of validity. Sublimation and melting pressures of dry ice are predicted accurately using Gibbs energies calculated from the new dry ice equation and from the fundamental equation by Span and Wagner for the fluid phase (J. Phys. Chem. Data 1996, 25, 1509À1596). The results agree with those of the reference equations for sublimation and melting pressure published by Span and Wagner mostly within the uncertainty given for these equations. The resulting sublimation and melting pressures are very sensitive to variations of the Gibbs energy. The use of another equation of state for the fluid phase has a significant impact on the calculated equilibrium pressures. It is shown that the equation for dry ice also might be used for the calculation of equilibria with dry ice in the solid phase and mixtures in the fluid phase.

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The COSMO-SAC modeling approach has found wide application in science as well as in a range of industries due to its good predictive capabilities. While other models for liquid phases, as for example UNIFAC, are in general more accurate than COSMO-SAC, these models typically contain many adjustable parameters and can be limited in their applicability. In contrast, the COSMO-SAC model only contains a few universal parameters and subdivides the molecular surface area into charged segments that interact with each other. In recent years, additional improvements to the construction of the sigma profiles and evaluation of activity coefficients have been made. In this work, we present a comprehensive description how to postprocess the results of a COSMO calculation through to the evaluation of thermodynamic properties. We also assembled a large database of COSMO files, consisting of 2261 compounds, freely available to academic and noncommercial users. We especially focus on the documentation of the implementation and provide the optimized source code in C++, wrappers in Python, sample sigma profiles calculated from each approach, as well as tests and validation results. The misunderstandings in the literature relating to COSMO-SAC are described and corrected. The computational efficiency of the implementation is demonstrated.