The structural relaxation of the alpha-Al2O3(0001) - an investigation of potential errors

All electron, first principles, periodic calculations have been carried out to investigate the relaxation of the Al-terminated corundum surface. Diffe rent theoretical formalisms, Hartree-Fock (HF) and density functional theor y using either the LDA or the hybrid B3LYP exchange-correlation functional, have been employed. In the past, many ab initio studies of surface structu re have been performed using the experimental, rather than the theoreticall y optimized bulk structures. In the current study, we show that this leads to significant differences in the predicted geometry. In addition, we demon strate that optimizing a limited subset of surface parameters also has a si gnificant effect on the accuracy of the final geometry. The extent of the e ffect associated with each of these sources is shown to be strongly depende nt on the choice of exchange-correlation potential. (C) 2001 Elsevier Scien ce B.V. All rights reserved.