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Issue 36, 2017
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Understanding the influence of low-frequency vibrations on the hydrogen bonds of acetic acid and acetamide dimers

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Abstract

Low-frequency vibrations coupled to high-frequency modes are known to influence the hydrogen bond strengths in a weakly interacting dimer. In this context, various acetic acid and acetamide dimers were analyzed using Møller–Plesset second-order perturbation (MP2) and density functional theory (DFT)-based approaches with explicit anharmonicity corrections. The computed low-frequency fundamentals as well as the high-frequency modes, which were found to be related to hydrogen bonding (OH/NH stretching modes), were analyzed and their computed intensities were correlated with their hydrogen-bond strengths/binding energies. There are similarities in the nature of eight low-frequency fundamentals of these two dimers, and the in-plane bending and stretch-bend fundamentals of the different dimers of these two species (in this low-frequency region) have specific roles in their relative stability order. The computed linear correlations were further verified against the results from coupled cluster calculations including triple excitation (CCSD(T)), Gaussian-G4 (G4), Gaussian-G2-MP2 (G2MP2) and complete basis set (CBS-QB3) methods of high accuracy energy calculations. As a consequence of such linear correlations, an additive property of local fragment energies (responsible for hydrogen bonding) was found to be a valid approximation to predict the binding energies of such dimers and the idea was found to be extendable to the other homologues of these acids/amides.

Graphical abstract: Understanding the influence of low-frequency vibrations on the hydrogen bonds of acetic acid and acetamide dimers

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Publication details

The article was received on 22 Jun 2017, accepted on 23 Aug 2017 and first published on 25 Aug 2017


Article type: Paper
DOI: 10.1039/C7CP04224H
Citation: Phys. Chem. Chem. Phys., 2017,19, 24866-24878
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    Understanding the influence of low-frequency vibrations on the hydrogen bonds of acetic acid and acetamide dimers

    C. Copeland, O. Menon, D. Majumdar, S. Roszak and J. Leszczynski, Phys. Chem. Chem. Phys., 2017, 19, 24866
    DOI: 10.1039/C7CP04224H

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