Direct Elucidation of the Vibrationally Averaged Structure of Benzene: A Path Integral Molecular Dynamics Study

Taro Udagawa; Hikaru Tanaka; Tsuneo Hirano; Kazuaki Kuwahata; Masanori Tachikawa; Masaaki Baba; Umpei Nagashima

doi:10.1021/acs.jpca.2c07197

Direct Elucidation of the Vibrationally Averaged Structure of Benzene: A Path Integral Molecular Dynamics Study

J Phys Chem A. 2023 Feb 2;127(4):894-901. doi: 10.1021/acs.jpca.2c07197. Epub 2023 Jan 22.

Authors

Taro Udagawa¹, Hikaru Tanaka¹, Tsuneo Hirano², Kazuaki Kuwahata³, Masanori Tachikawa³, Masaaki Baba^{3

4}, Umpei Nagashima³

Affiliations

¹ Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University, Yanagido 1-1, Gifu501-1193, Japan.
² Department of Chemistry, Faculty of Science, Ochanomizu University, 2-1-1 Otsuka, Bunkyo-ku, Tokyo112-8610, Japan.
³ Graduate School of NanobioScience, Yokohama City University, 22-2 Seto, Kanazawa-ku, Yokohama236-0027, Japan.
⁴ Molecular Photoscience Research Center, Kobe University, Nada-ku, Kobe657-8501, Japan.

PMID: 36683277
DOI: 10.1021/acs.jpca.2c07197

Abstract

Path integral molecular dynamics (PIMD) simulations for C₆H₆, C₆D₆, and C₆T₆ have been carried out to directly estimate the distribution of projected C-H(D,T) bond lengths onto the principal axis plane. The average values of raw C-H(D,T) bond lengths obtained from PIMD simulations are in the order of ⟨R_C-H⟩ > ⟨R_C-D⟩ > ⟨R_C-T⟩ due to the anharmonicity of the potential energy curve. However, the projected C-H(D,T) bond lengths are almost the same as those reported by Hirano et al. [J. Mol. Struct. 2021, 1243, 130537]. Our PIMD simulations directly and strongly support the explanation by Hirano et al. for the experimental observations that almost the same projected C-H(D) bond lengths are found for C₆H₆ and C₆D₆. The PIMD simulations also predicted the same projected bond lengths for C₆T₆ as those of C₆H(D)₆. In addition to the previous local mode analysis, the present PIMD simulations predicted, for benzene isotopologues, that the vibrationally averaged structure is planar but non-flat.