Abstract
Total-energy and force calculations have been performed for thin overlayers of GaAs on a Si(111) substrate. The calculated atomic positions are compared with recent x-ray standing-wave measurements. The atomic positions obtained for the structure in which the stacking sequence is...SiSiGaAsSiAs are in the best agreement with the x-ray standing-wave measurements. This structure has a significantly lower total energy than the structure...SiSiSiAsGaAs.