Local Geometry of Tetrahedrally Coordinated Boron Correlates with 11B NMR Chemical Shifts in Borosilicate Minerals

Chemical shifts from the 11B nuclear magnetic resonance (NMR) spectra of crystalline borosilicate minerals with highly ordered, tetrahedrally coordinated boron atoms (B) linearly correlate with the local geometric parameters related to the B-O-T angles (T denotes a tetrahedrally coordinated atom) obtained from single-crystal X-ray diffraction. The correlations between the 11B NMR chemical shifts and structural parameters are similar in functional form to the well-known correlations of 29Si and 27Al NMR chemical shifts with structural features of silicates and aluminosilicates, respectively. These correlations enable the use of 11B NMR chemical shifts to elucidate the local geometry of tetrahedrally coordinated B and aid in establishing B ordering among the crystallographic T-sites within crystalline borosilicates.