All species in this reaction system were fully optimized at B3LYP/6-31G(d

p) basis set level by using density functional theory

and then single point energy calculations were performed.In succession the hydrolysis and oligomerization mechanisms of Si(OCH3)4 in acidic solutions were investigated systematically to elucidate the competitiveness between hydrolysis and oligomerization.This theoretical model show that:(1) H2O is bonded to precursors via hydrogen bonds or coordination bonds to facilitate hydrolysis;(2) H2O attacks precursors from the opposite side of protonated alkoxy groups;(3) for the fourth-order hydrolysis

H2O expels protonated alkoxy groups from the opposite side

but the precursor does not hydrolyze completely;(4) the hydrolysis products condense via the ring mode

viz. the hydrolysis products are linked together via hydrogen bonds to form polyatomic rings to oligomerize via hydrogen transfer;(5) the precursor Si(OCH3)4 is inclined to hydrolyze than to condense;(6) proton blocks the cationic dimers to cyclize;(7) silicon cation can solicit non-barrier oligomerization

but the ionic reaction channels are energetically unfavorable.