2004-08-18Zeitschriftenartikel DOI: 10.1039/b412795a
Environmental effects on vibrational proton dynamics in H5O2+: DFT study on crystalline H5O2+ClO4–
Mathematisch-Naturwissenschaftliche Fakultät I
The structure as well as IR and inelastic neutron scattering (INS) spectra of H5O2+ in crystalline H5O2+ClO4– were simulated using Car–Parrinello molecular dynamics with the BLYP functional. The potential of the OH+O fragment is very shallow. The Pnma structure, assumed in the X-ray study to be the most suitable choice, is a saddle point on the potential energy surface, while the P212121 minimum structure is only 20 cm–1 lower in energy. The computed INS and IR spectra enable us to achieve a complete assignment of the observed spectra. The broad band between 1000 and 1400 cm–1 is due to the asymmetric stretch and one of the bending vibrations of the OH+O fragment, while the band between 1600 and 1800 cm–1 is due to the bending vibration of the water molecules and the second bending of the OH+O fragment. Comparison with the vibrational spectra of isolated H5O2+, obtained using Born–Oppenheimer molecular dynamics simulation, reveals environmental effects on vibrational proton dynamics in strong H-bonded species. The most pronounced changes are found for the OH+O bending modes because the two bending coordinates become distinctly different for the structure that the H5O2+ ion assumes in the crystal.
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