9705746 Oldfield The PIs on this proposal will use ab initio density functional methods and a cluster of RISC work stations to computer parameter surfaces relating spectroscopic observables and structure in silicate systems, for example how the chemical shift or quadrupole coupling constant of a bridging oxygen varies with bond length and bond angle. These can then be used to deduce, e.g., the distributions of M-O bond lengths and M-O-M bond angles in disordered and amorphous phases. They will focus their efforts on oxide systems based on Si, Al, B, and P (including mixed heteroatom systems; e.g. aluminosilicates). The NMR parameters can be calculated for all of these cations and for 17-O, and for all of them there is a good experimental data base to verify the calculations. The parameter surfaces will be the first of their type and will be calculated at a sufficiently high level that they will be of general quantitative applicability for a wide range of applications.
