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

We report the results of first principles density functional theory (DFT) c alculations 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 o r of the geminal = Si(H)(2) and = Si(OH)(2) defects has been fully optimize d from mechanically embedded cluster models derived from crystalline cr-qua rtz and the nuclear magnetic shielding properties have been determined acco rding 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) 200 0 Elsevier Science B.V. All rights reserved.