Molecular dynamics simulations of Na deposition on the TiO2(110) surface

A computational study of the sodium deposition on the TiO2(110) rutile surface was carried out. Using both molecular dynamics methods and complementary ab initio Hartree-Fock embedded cluster calculations, the Na arrangements on the surface for coverages up to theta = 0.5 ML were considered. Our simulations show that Na adsorbs on the surface binding three oxygen atoms, two protruded and one basal, in a quasi-symmetric configuration. This coordination type is found whatever the coverage, in agreement with previous experimental and theoretical works. The Na atoms are found to be arranged in an alternated disposition around the protruded oxygen atom rows. This distribution is almost perfect for a theta = 0.25 ML coverage, since coadsorption effects are small and the Na atoms find place enough to be accommodated. For a coverage of theta = 0.5 ML, some islands, in which the Na atoms are facing each other across two protruded oxygen atoms, are found, even in long time simulations, Formation of Na2O dimers was not observed. (C) 1998 Elsevier Science B.V. All rights reserved.