Multiconfigurational self-consistent field calculations have been performed to investigate structural and electronic properties of cubic silicon carbide (001) (SiC (001)) surfaces. The dimer on silicon-terminated SiC (001) (Si-SiC (001)) is found to be diradical in nature, due to destabilization of the pi bond by bending the dimer. Since the SiC lattice constant is larger than that of diamond, the >C=C< dimer on the carbon-terminated SiC (001) (C-SiC (001)) surface is flatter and its pi bond is stronger than those on diamond (001). The bridging dimer on the C-SiC (001) exhibits relatively small multiconfigurational character despite its bent geometry. H-2 adsorption onto the Si-SiC (001) diradical dimer is more favorable than that onto the partial pi bonded Si (001) dimer. As the dimer geometry becomes flatter, the pi bond becomes stronger and the H-2 adsorption on the dimer becomes less favorable. (C) 2003 American Institute of Physics.