Structure and stability of nonpolar surfaces in 4H- and 6H-SiC have been investigated within the framework of a self-consistent charge density functional based tight binding method. The lowest energy stoichiometric surface is corrugated for (10 (1) over bar0) but atomically smooth for (11 (2) over bar0). The most stable clean surfaces are Si rich. independent of the growth conditions. Unlike the polar surfaces both nonpolar surfaces can completely be passivated by a single SiO2 adlayer
