A reaction pathway for water adsorption on Si(100)(2x1)

We present ab initio investigations for the reaction pathway between gas phase water and the Si(100)(2x1) surface. The results indicate that there is no barrier for adsorption and that the mechanism of dissociation occurs by molecular physisorption. However, the chemisorption process is very favorable (by Delta E=-2.14 eV) and the barrier is very small (Delta E=+0.01 eV). We show that the oxygen attack is efficient from any position of water colliding with the surface dimer, and that the interaction between the molecule and the surface begins earlier than estimated previously.