Journal of the American Chemical Society, Vol.126, No.33, 10450-10456, 2004
Xe chemical shift tensor in silicalite and SSZ-24
We report, for the first time, a theoretical prediction of the Xe-129 nuclear magnetic resonance chemical shift tensor of xenon atom in a single crystal of silicalite at near-zero occupancy and the temperature dependence of the Xe NMR chemical shift tensor for the polycrystalline silicalite at maximum occupancy. The former is a measure of the sensitivity of the Xe tensor components to the local structure of the channels without Xe-Xe contributions. The latter is a measure of the sensitivity of the Xe-Xe tensor components to the Xe-Xe distributions, as determined by the Xe-Xe potential function in competition with the Xe-silicalite potential function. Both theoretical predictions can be compared against Xe NMR experiments: the first against the Xe spectra collected as a function of rotation of the single crystal about the three crystalline axes in a magnetic field, and the second against variable temperature Xe NMR studies (below room temperature) of polycrystalline silicalite at maximum Xe occupancy. With the same parameter set (Xe-O potential and shielding functions), we predict the line shapes of Xe in SSZ-24 zeolite under various conditions of occupancy and temperature.