|French, Alfred - Al|
Submitted to: American Chemical Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 1/15/2006
Publication Date: 3/31/2006
Citation: French, A.D., Johnson, G.P. 2006. Roles of starting geometries in quantum mechanics studies of cellobiose. American Chemical Society Abstracts. CELL 16.
Technical Abstract: Recently we studied the conformations of cellobiose with HF/6-31G(d) energy minimization by constructing an adiabatic energy surface for the region that contains most of the geometries that are observed in crystals. Single point HF/6-311+G(d) calculations were also carried out. We also looked at two other regions with unconstrained minimization, one of which corresponds to the lowest energy as reported by Strati et al., as well as another local minimum. Two sub-regions covered by the adiabatic were also given unconstrained minimizations. B3LYP/6-31+G(d) minimizations and B3LYP/6-311+G(d) calculations were also carried out for these four locations. Because of the effect of the orientation of the exo-cyclic groups on the calculated energies, 181 different combinations of these side-group orientations (starting geometries) were tried at each of the points on the adiabatic map, and 155 combinations for the unconstrained minimizations. Altogether, more than 15,000 energy minimizations were carried out. This presentation will explore how the different starting geometries contributed to the overall results, and how some modeled structures may be unrealistic.