Résumé
A combination of classical molecular dynamics (MD) and ab initio
Car-Parrinello molecular dynamics (CPMD) simulations is used to investigate the
adsorption of water on a free amorphous silica surface. From the classical MD
SiO_2 configurations with a free surface are generated which are then used as
starting configurations for the CPMD.We study the reaction of a water molecule
with a two-membered ring at the temperature T=300K. We show that the result of
this reaction is the formation of two silanol groups on the surface. The
activation energy of the reaction is estimated and it is shown that the
reaction is exothermic.