College Park, Maryland June 6 - 10 , 2004 |
MP9: Short Strong Hydrogen potential surfaces studied by INS
Timothy Jenkins, Bruce Hudson, Damian Allis, Jenn Ciezak (Syracuse University, Syracuse, NY), Dale Braden (Schrödinger Inc., Portland, OR)
Symmetric hydrogen bonds (e.g., O-H…O) have equivalent local minima for the H atom positions separated by a barrier at the position of equal O-H-O lengths. This barrier decreases in height as the O-O distances and apparently vanishes for sufficiently short distances. The short, strong hydrogen bonds that occur for small O-O distances are also known as “low barrier” hydrogen bonds. These systems were expected to display a failure of the harmonic dynamical treatment due to the anharmonic nature of the short, strong hydrogen bonds. We examined several co-crystals of varying O-O distances and both intermolecular and intramolecular hydrogen bonds by vibrational spectroscopy to provide a high-resolution basis calculation comparison. Neutron vibrational spectroscopy results are presented. Comparison calculations involving the short, strong hydrogen bond potential surfaces were also carried out using density functional methods. Potential surface models suggest that the surface is best fit by a quartic model resulting in agreement to the vibrational spectra. Vibrational spectrums were determined using FANS at NIST and TOSCA at ISIS, RAL.
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