Car–Parrinello simulation of H2O dissociation on rutile

Chemisorption and physical adsorption of H2O at the (1 0 0) and (1 1 0) surfaces of the rutile modification of TiO2 have been studied using the Car–Parrinello method. Spontaneous dissociation was observed in the simulation when a water molecule was inserted into a vacancy on the partially reduced (1 0 0) surface. On the partially reduced (1 1 0) surface no spontaneous dissociation took place but hydroxylated configurations were stable. The perfect rutile surfaces adsorbed undissociated water forming a stable Ti–O bond and one hydrogen bond. When starting from two hydroxyl groups fast recombination was observed. The relaxation of the non-hydroxylated (1 1 0)-surface was studied by molecular dynamics and a soft surface phonon at 380 cm−1 was found.