Comparison of ab initio and empirical approaches to the quartz surface

We investigate several possible reconstructions of the (0 0 1) alpha-quartz surface by using a combinatory approach of classical and ab initio molecul ar dynamics (MD). Configurational space is efficiently explored by fast cla ssical MD simulations with a semi-empirical three-body potential, which has been shown to be accurate in simulations of the bulk. These runs generate initial structures for further refinement by the accurate quantum MD method of Car-Parrinello (P. Car. M. Parrinello, Phys. Rev. Lett. 55 (1985) 2471) . Stable reconstructions of the quartz surface have been produced. They sho w the same pattern: formation of six- and three-membered rings. The obtaine d structures were found to be local minima in the classical potential, ther eby demonstrating the usefulness of the empirical potential for surface cal culations. (C) 2000 Elsevier Science B.V. All rights reserved.