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Updated: Jun 25, 2026

An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids
Published on: December 4, 2017
Least popular vibrational entropy model provides the best accuracy and robustness
Julia A Velmiskina1, Vadim I Malyshev1, Igor S Gerasimov1
1N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., 119991 Moscow, Russian Federation.
Abstract:
Vibrational contributions into free energies usually amount to several kcal/mol and can significantly affect computational predictions. However, they are generally estimated incorrectly for chemical systems in solutions because the usual (employed in ∼99% of cases) models of vibrational entropies are extremely sensitive to errors in low-lying frequencies (below 300 cm-1), and these low-lying frequencies involve solvent molecules that are usually neglected (computed implicitly) in quantum chemical calculations. We find that only one vibrational entropy approximation-the one proposed by Truhlar in 2011-which is used in only ∼2% of cases, is stable in the low-lying frequency region and does not exhibit this problem. Accordingly, this approximation shows the best accuracy and robustness on a diverse set of experimental complexation energies and can be somewhat improved even further.
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