Critical interpretation of CH- and OH- stretching regions for infrared spectra of methanol clusters (CH₃OH)n (n = 2-5) using self-consistent-charge density functional tight-binding molecular dynamics simulations

Yoshifumi Nishimura, Yuan Pern Lee, Stephan Irle, Henryk A. Witek

研究成果: Article査読

17 被引用数 (Scopus)

抄録

Vibrational infrared (IR) spectra of gas-phase O-H⋅⋅⋅O methanol clusters up to pentamer are simulated using self-consistent-charge density functional tight-binding method using two distinct methodologies: standard normal mode analysis and Fourier transform of the dipole time-correlation function. The twofold simulations aim at the direct critical assignment of the C-H stretching region of the recently recorded experimental spectra [H.-L. Han, C. Camacho, H. A. Witek, and Y.-P. Lee, J. Chem. Phys. 134, 144309 (2011)]. Both approaches confirm the previous assignment (ibid.) of the C-H stretching bands based on the B3LYP/ANO1 harmonic frequencies, showing that ν3, ν9, and ν2 C-H stretching modes of the proton-accepting (PA) and proton-donating (PD) methanol monomers experience only small splittings upon the cluster formation. This finding is in sharp discord with the assignment based on anharmonic B3LYP/VPT2/ANO1 vibrational frequencies (ibid.), suggesting that some procedural faults, likely related to the breakdown of the perturbational vibrational treatment, led the anharmonic calculations astray. The IR spectra based on the Fourier transform of the dipole time-correlation function include new, previously unaccounted for physical factors such as non-zero temperature of the system and large amplitude motions of the clusters. The elevation of temperature results in a considerable non-homogeneous broadening of the observed IR signals, while the presence of large-amplitude motions (methyl group rotations and PA-PD flipping), somewhat surprisingly, does not introduce any new features in the spectrum.

本文言語English
論文番号094303
ページ(範囲)94303
ページ数1
ジャーナルThe Journal of Chemical Physics
141
9
DOI
出版ステータスPublished - 2014 9月 7
外部発表はい

ASJC Scopus subject areas

  • 物理学および天文学(全般)
  • 物理化学および理論化学

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