Abstract
Deposition of magnesia on (00.1) alumina substrates forms a topotaxial (00.1)[1 (1) over bar.0] Al2O3 / (111)[1 (1) over bar 0]MgO interface and subsequent heat treatment an epitaxial, intermediate layer of MgAl2O4-spinel with the orientation relationship (111)[1 (1) over bar 0]. This solid-solid-phase transformation reduces the misfit of the lattice parameters from 5.8% to 3.7% and is formed by the mutual cation diffusion of Mg2+ and Al3+, while the Oxygen sublattice remains nearly unchanged. With molecular dynamics simulations the atomic structure and the thermodynamic data, like Gibbs free energy, interface energy and driving force of this system are calculated using a new approach: The different, subsequent stages of the phase transformation are calculated separately by an individual input of supercells, which is admitted, because the result of the transformation is known from the experiment.