Materials Chemistry, The Ångström Laboratory,Uppsala University, Box 538, S-751 21 Uppsala, Sweden
|I will discuss the calculation of OH frequencies in ionic aqueous solutions and in crystalline solids, absolute frequencies as well as frequency shifts.|
O-H stretching vibrational frequencies are known to be very sensitive to intermolecular interaction. IR and Raman spetroscopies are therefore two of the major research tools for characterization of the local structure and bonding around water and OH groups.
Theoretical calculations can provide much insight here, and help disentangle the various contributions to the OH frequency downshift (down or up).
The calculation of OH frequencies in liquid solutions is particularly challenging since it requires an adequate treatment of the temperature effects, the interatomic interactions, the (anharmonic) vibrations, and access to a reliable structural model. We are using a 4-step "QM + MD + QM + QM' strategy to address these computational difficulties, and I will present results for the first hydration shell around mono- and multi-valent metal ions in aqueous solution.