Ab initio calculations of 29Si solid state NMR chemical shifts of silane and silanol groups in silica

We report the results of first principles density functional theory (DFT) calculations on the H-1 and Si-29 NMR chemical shifts of silane and hydroxyl groups in silica. The structure of the isolated drop Si-H and drop Si-OH or of the geminal = Si(H)(2) and = Si(OH)(2) defects has been fully optimized from mechanically embedded cluster models derived from crystalline cr-quartz and the nuclear magnetic shielding properties have been determined according to the GIAO method, The computed Si-29 chemical shifts, delta(Si-29) in ppm, are (in parenthesis the experimental values): drop Si-OH -99 (-99), drop Si-H -86 (-85), = Si(OH)(2) -85 (-89), = Si-(H)(2) -55 (-50). (C) 2000 Elsevier Science B.V. All rights reserved.