標題: 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
作者: Nishimura, Yoshifumi
Lee, Yuan-Pern
Irle, Stephan
Witek, Henryk A.
交大名義發表
應用化學系
應用化學系分子科學碩博班
National Chiao Tung University
Department of Applied Chemistry
Institute of Molecular science
公開日期: 7-Sep-2014
摘要: Vibrational infrared (IR) spectra of gas-phase O-H center dot center dot center dot 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 nu(3), nu(9), and nu(2) 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. (C) 2014 AIP Publishing LLC.
URI: http://dx.doi.org/10.1063/1.4893952
http://hdl.handle.net/11536/25181
ISSN: 0021-9606
DOI: 10.1063/1.4893952
期刊: JOURNAL OF CHEMICAL PHYSICS
Volume: 141
Issue: 9
結束頁: 
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