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Issue 24, 2017
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Ethylperoxy radical: approaching spectroscopic accuracy via coupled-cluster theory

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Abstract

Interest in peroxy radicals derives from their central role in tropospheric and low-temperature combustion processes; however, their transient nature limits the scope of possible experimental characterization. As a result, theoretical methods (notably, coupled-cluster theory) have become indispensable in the reliable prediction of properties of such ephemeral open-shell systems. Herein, the [X with combining tilde] and à state conformers of ethylperoxy radical (C2H5O2) have been structurally optimized at the CCSD(T)/ANO2 level of theory. Relative enthalpies at 0 K [including à ← [X with combining tilde] transition origins (T0)] are reported, incorporating CCSD(T) electronic energies extrapolated to the complete basis set limit via the focal point approach. Higher-level computations, employing basis sets as large as cc-pV5Z and post-HF methods up to CCSDT(Q), prove essential in achieving predictions to within 10 cm−1 for experimental T0; we predict 7363 and 7583 cm−1 for the trans and gauche conformers, respectively. Furthermore, predictions of [X with combining tilde] state fundamental transitions incorporating CCSD(T)/ANO0 anharmonic contributions are given. For each conformer, all 21 modes were characterized, improving upon the 16 modes reported in the experimental literature, and providing predictions for the 5 remaining modes.

Graphical abstract: Ethylperoxy radical: approaching spectroscopic accuracy via coupled-cluster theory

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Publication details

The article was received on 28 Apr 2017, accepted on 31 May 2017 and first published on 31 May 2017


Article type: Paper
DOI: 10.1039/C7CP02795H
Citation: Phys. Chem. Chem. Phys., 2017,19, 15715-15723
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    Ethylperoxy radical: approaching spectroscopic accuracy via coupled-cluster theory

    A. M. Launder, J. M. Turney, J. Agarwal and H. F. Schaefer, Phys. Chem. Chem. Phys., 2017, 19, 15715
    DOI: 10.1039/C7CP02795H

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