COSMO-RS - The thermodynamic theory of COSMOtherm

What is COSMO-RS?

COSMO-RS is a theory (i.e. a set of equations) to calculate the chemical potential differences of molecules in liquids. This chemical potential difference will be transformed into properties such as solubilities, activities or vapor pressures. In this regard, COSMO-RS can be compared to gE-models like UNIFAC or NRTL. The main advantage of COSMO-RS is that it uses quantum chemically generated charge density surfaces to describe each molecule and its interactions with other molecules. It is thus applicable without group parameters or any system-specific adjustments, and automatically incorporates electronic group effects such as inductive and mesomeric influences on the polarity as well as intramolecular interactions such as hydrogen bonding.

Primary application range

  • Incompressible liquids and ideal gases (not near the critical point)
  • Equilibrium properties (not kinetically controlled effects)
  • Small to medium sized solute molecules (up to ~800 Dalton)
  • Temperatures between 170 K to 600 K

Extended application range

  • QSPR-based partitioning on poorly defined matter, e.g. adsorption on active carbon
  • Critical systems by applying equations of state
  • Pseudo-liquid systems, e.g. solubility in polymers
  • Secondary properties like pka or interfacial tension
  • Partitioning in micellar systems
  • QSPR-based non-equilibrium properties (flash point, pure compound viscosity)


  • Is a gE model
  • Is based on quantum chemistry (COSMO)
  • Requires no group parameters
  • Requires no system-specific adjustments
  • Uses a single parameter set for all properties

More information

Read more about COSMO-RS in this
introductory presentation or join one of our free workshops.


"Conductor-like Screening Model for Real Solvents: A New Approach to the Quantitative Calculation of Solvation Phenomena", A. Klamt - The Journal of Physical Chemistry, 1995, vol. 99, no7, pp. 2224-223, DOI: 10.1021/j100007a062

"Refinement and Parametrization of COSMO-RS", A. Klamt, V. Jonas, T. B├╝rger, JCW Lohrenz - J. Phys. Chem. A, J. Phys. Chem. A, 102 (26), 5074 -5085, 1998, DOI: 10.1021/jp980017s

"COSMO-RS: From Quantum Chemistry to Fluid Phase Thermodynamics and Drug Design", A. Klamt, Elsevier Science Ltd., Amsterdam, The Netherlands (2005), ISBN: 0-444-51994-7.

"The COSMO and COSMO-RS solvation models", A. Klamt, Wiley Interdisciplinary Reviews: Computational Molecular Science. WIREs Comput Mol Sci 2011 1 699-709, DOI: 10.1002/wcms.56