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COSMO-SAC: Open-Source Implementation
- Fig. 1 A three-dimensional view of ethanol and its segment charge densities
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The design of technical processes and plants in the chemical industry requires a profound knowledge of thermodynamic properties, i.e. for pure substances or multicomponent mixtures. Conducting experimental measurements requires a lot of effort in time and money, especially when dealing with extreme conditions or toxic fluids.
Therefore, many models have been developed to predict the thermodynamic behavior of fluids. Predictive models, such as the UNIFAC that are based on the group-contribution method (GCM), are now complemented by a more predictive alternative that is based on quantum mechanical conductor-like screening model (COSMO) calculations, originally proposed by Klamt et al. (conductor-like screening model for real solvents, COSMO-RS).
Based on the COSMO-RS model, Lin and Sandler developed the COSMO segment activity coeﬃcient model (COSMO-SAC). In these models, the interactions of molecules in a mixture are not modeled as pairwise molecular group interactions but rather as pairwise interactions of charged surface segments of the molecule that can be obtained from quantum mechanical calculations when the molecule is placed in a perfect conductor.
A large database of COSMO ﬁles, consisting of 2261 compounds, is freely available to academic and noncommercial users. (Link to Database )