Molecular dynamics simulation of the (0001)α-Al2O3 and α-Cr2O3 surfaces

A simple, rigid pair-potential model is applied to investigate the dynamics of the (0001) alpha-Al2O3 and alpha-Cr2O3 surfaces using the molecular dynamics technique. The simulations employ a two-stage equilibration process: in the first stage the simulation-cell size is determined via the constant-stress ensemble, and in the second stage the equilibration of the size-corrected simulation cell is continued in the canonical ensemble. The thermal expansion coefficients of bulk alumina and chromia are evaluated as a function of temperature. Furthermore, the surface relaxation and mean-square displacement of the atoms versus depth into the slab are calculated, and their behaviour in the surface region analysed in detail. The calculations show that even moderate temperatures (similar to 400 degrees C) give rise to displacements of the atoms at the surface which are similar to the lattice mismatch between alpha-alumina and chromia. This will help in the initial nucleation stage during thin film growth, and thus facilitate the deposition of alpha-Al2O3 on (0001) alpha-Cr2O3 templates. (c) 2007 Elsevier B.V. All rights reserved.