Calculation of the two-dimensional non-separable partition function for two molecular systems

• Published in: Journal of molecular modeling 2014-04, Vol.20 (4), p.2190-2190, Article 2190
• Main Authors: Simón-Carballido, Luis, Fernández-Ramos, Antonio
• Format: Article
• Language: English
• Subjects: Algorithms; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Computer Appl. in Life Sciences; Computer Applications in Chemistry; Models, Theoretical; Molecular Medicine; Original Paper; Quantum Theory; Theoretical and Computational Chemistry; Topical Collection QUITEL 2013
• ISSN: 1610-2940; 0948-5023
• DOI: 10.1007/s00894-014-2190-z

We present the application of an accurate quantum treatment, called two-dimensional non-separable (2D-NS), to the calculation of internal rotation partition functions of molecules with two rotors. This methodology involves full coupling in the kinetic and potential energies; the later is written as a Fourier series type potential. The resulting Hamiltonian is introduced in the Schrödinger equation and solved by the variational method. The method was applied to the 2-propenol and to the 3-fluoro-2-propenol molecular systems. The former molecule presents weak coupling between the torsion, whereas the later is an example of strong coupling. The comparison of 2D-NS with one-dimensional accurate models that involve separation of the two torsions, indicate that a separable model is inadequate to study systems in the strong coupling regime. The results indicate that for the case of strong coupling the multi-conformer harmonic approximation gives better results than a separable anharmonic model.