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Potential energy surfaces and vibrational spectra of H 5 O 2 + and larger hydrated proton complexes
Author(s) -
Ojamäe Lars,
Shavitt Isaiah,
Singer Sherwin J.
Publication year - 1995
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560560872
Subject(s) - anharmonicity , chemistry , potential energy surface , basis set , potential energy , molecular physics , proton , ab initio , ab initio quantum chemistry methods , atomic physics , spectral line , binding energy , density functional theory , computational chemistry , molecule , physics , condensed matter physics , quantum mechanics , organic chemistry
This article presents calculations of the structure, binding energetics, potential energy surfaces, and vibrational spectra of the H 5 O 2 +ion. The 15‐dimensional potential energy surface for the seven nuclei in the ionic complex was computed by pointwise ab initio Møller‐Plesset second‐order perturbation (MP2) calculations, using the correlation‐consistent pVTZ basis set augmented with diffuse basis functions on oxygen. The potential energy surface for the proton‐transfer mechanism was investigated, and the effects of surrounding water molecules on the proton‐transfer potential energy curve was studied. Density functional calculations for the proton‐transfer potential surface are compared to the MP2 results. Geometry‐optimized structures, binding energies, and harmonic vibrational spectra of H 5 O 2 +and H 9 O 4 +are presented. The energy‐minimum structure of H 5 O 2 +using the augmented pVTZ basis set is of C 2 symmetry, whereas for H 9 O 4 + , using the TZ2P basis set, it is of C 3 symmetry. The H‐bonded OH stretching harmonic frequency of H 5 O 2 +is very low, 913 cm −1 , whereas for H 9 O 4 +it is 2927 cm −1 . The subspace spanned by the hydrogen‐bonded OH distance and the OO distance were used in one‐ and two‐dimensional calculations of the anharmonic vibrational spectrum using collocation methods. The coupling of the OH stretch with the OO vibration causes a redshift and the anharmonicity a blueshift of the OH frequency: the resulting fundamental frequency of the H‐bonded OH vibration is 1275 cm −1 . Zero‐point energies of the proton vibration and pathways for exchange of protons within H 5 O 2 +are discussed. © 1995 John Wiley & Sons, Inc.