Car-Parrinello simulation of H2O dissociation on rutile

Chemisorption and physical adsorption of H2O at the (10 0) and (I 10) 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 (10 0) surface. On the partially reduced (110) 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 (11 0)-surface was studied by molecular dynamics and a soft surface phonon at 380 cm(-1) was found. (C) 2001 Elsevier Science B.V. All rights reserved.