Different structures give similar vibrational spectra: The case of OH− in aqueous solution

Authors: Pavlin D. Mitev, Philippe A. Bopp, Jasmina Petreska, Kaline Coutinho, Hans Ågren, Ljupco Pejov, and Kersti Hermansson

We have calculated the anp5aharmonic OH(aq) vibrational spectrum in aqueous solution with a “classical Monte Carlo simulation + QM/MM + vibrational” sequential approach. A new interaction model was used in the Monte Carlo simulations: a modified version of the charged-ring hydroxide-water model from the literature. This spectrum is compared with experiment and with a spectrum based on CPMD-generated structures, and the hydration structures and H-bonding for the two models are compared. We find that: (i) the solvent-induced frequency shift as well as the absolute OH frequency are in good agreement with experiment using the two models; (ii) the Raman and IR bands are very similar, in agreement with experiment; (iii) the hydration structure and H-bonding around the ion are very different with the two ion-water interaction models (charged-ring and CPMD); (iv) a cancellation effect between different regions of the hydration shell makes the total spectra similar for the two interaction models, although their hydration structures are different; (v) the net OH frequency shift is a blueshift of about +80 cm−1 with respect to frequency of the gas-phase ion.

J. Chem. Phys. 138, 064503 (2013);

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