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Relative electronic and free energies of octane's unique conformations

  • This study reports the geometries and electronic energies of n-octane's unique conformations using perturbation methods that best mimic CCSD(T) results. In total, the fully optimised minima of n-butane (2 conformations), n-pentane (4 conformations), n-hexane (12 conformations) and n-octane (96 conformations) were investigated at several different theory levels and basis sets. We find that DF-MP2.5/aug-cc-pVTZ is in very good agreement with the more expensive CCSD(T) results. At this level, we can clearly confirm the 96 stable minima which were previously found using a reparameterised density functional theory (DFT). Excellent agreement was found between their DFT results and our DF-MP2.5 perturbation results. Subsequent Gibbs free energy calculations, using scaled MP2/aug-cc-pVTZ zero-point vibrational energy and frequencies, indicate a significant temperature dependency of the relative energies, with a change in the predicted global minimum. The results of this work will be important for future computational investigations of fuel-related octane reactions and for optimisation of molecular force fields (e.g. lipids).

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Document Type:Article
Author:Karl N. Kirschner, Wolfgang Heiden, Dirk Reith
Parent Title (English):Molecular Physics
First Page:1155
Last Page:1165
Publisher:Taylor & Francis
Date of first publication:2016/12/14
Tag:Alkane; MP2.5; fuel; hydrocarbon; lipid; octane; quantum mechanics
Departments, institutes and facilities:Fachbereich Informatik
Fachbereich Elektrotechnik, Maschinenbau, Technikjournalismus
Institut für Technik, Ressourcenschonung und Energieeffizienz (TREE)
Institute of Visual Computing (IVC)
Institut für funktionale Gen-Analytik (IFGA)
Dewey Decimal Classification (DDC):5 Naturwissenschaften und Mathematik / 53 Physik / 530 Physik
Entry in this database:2017/01/06