title: Local structure and chemical shifts for six-coordinated silicon in high-pressure mantle phases.
abstract: Most of the earth's mantle is made up of high-pressure silicate minerals that contain octahedrally coordinated silicon (Si(VI)), but many thermodynamically important details of cation site ordering remain unknown. Silicon-29 nuclear magnetic resonance (NMR) spectroscopy is potentially very useful for determining short-range structure. A systematic study of silicon-29 chemical shifts for Si(VI) has revealed empirical correlations between shift and structure that are useful in understanding several new calcium silicates. The observed ordering state of a number of high-pressure magnesium silicates is consistent with the results of previous x-ray diffraction studies.
authors.forename: J F
authors.initials: JF
authors.lastname: Stebbins
authors.forename: M
authors.initials: M
authors.lastname: Kanzaki