Physical Sciences and Mathematics Commons^™

Brominated aromatics, used extensively as flame retardants, have been studied with 81Br nuclear quadrupole resonance (NQR) spectroscopy. NQR requires lengthy frequency searches because 81Br NQR transition frequencies in brominated aromatics are spread over a wide (40 MHz) range. We investigate the ability of ab initio calculations to narrow this search range by predicting 81Br NQR transition frequencies for a series of brominated aromatics, using restricted Hartree−Fock (RHF) and Becke's three-parameter Lee−Yang−Parr density functional theory hybrid method (B3LYP). Basis sets used are of double and triple-ζ quality with varying degrees of polarization included on bromine. Geometries are the isolated molecules, with …

Andalusite, Al2SiO5, contains 5- and 6-coordinate aluminum sites, and is a preeminent model for 27 Al NMR spectroscopy. We describe a combined NMR, crystallography, and theory project:  single-crystal 27 Al NMR spectra at 298 K, the crystal structure of andalusite at 115 K, and electric field gradient calculations. The low-symmetry 5-coordinate site is a stiff test of the computational methods. In addition, the chemical shift tensor is measured for the 5-coordinate site. The small body of 27 Al NMR data, especially for rare 5-coordinate sites, inspires the calculation of NMR parameters. We explore the accuracy of two approaches for 27 …