Metal oxide surface dynamics from molecular dynamics simulations:: the α-Al2O3(0001) surface

Constant-stress, constant-temperature (10, 300 and 700 K) molecular dynamics simulations were carried out with shell-model potentials for an infinite crystalline A-terminated alpha -Al2O3(000 1) slab of similar to 25 Angstrom thickness. The surface undergoes considerable relaxation at 10 K, but exhibits ordered surface structures at all three temperatures. The relaxation causes the (0 0 0 1) surface at 10 K to appear oxygen-terminated. The ionic motion within the central and surface regions of the slab system has been analysed in terms of mean-square displacements. At room temperature the (u(2))(surface)/(u(2))(bulk) ratio for the Al ions is approximate to2.5 and when only the out-of-plane surface motion is considered the ratio is as large as approximate to3.5. The O ion motion at the surface is slightly smaller than that of the cations. (C) 2001 Elsevier Science B.V. All rights reserved.