Ab initio dynamics of the reaction pathway for dissociation of H2O and hydroxylation of Si surface. A thermalized mixture of H2O molecules experiences dissociation facilitated by collision with a semiconductor Si(111):H surface. Red, green, and blue spheres correspond to Si, O, and H atoms. Grey clouds represent isosurfaces of total charge density updated each femtosecond. Calculations are done with PW91 functional in plane-wave basis, with VASP software.