Bulk and surface electronic structure of hexagonal WC

The bulk and surface electronic structure of hexagonal WC have been investigated by self-consistent scalar relativistic calculations that apply the linear augmented-plane-wave method. The surface studies consider WC(0001)-W(1 x 1) and -C(1 x 1) faces and assume a slab geometry with bulk interlayer spacings. Separate calculations have been carried out for symmetrical nine-layer slabs containing either W(1 x 1) or C(1 x 1) surfaces and an asymmetrical eight-layer slab containing both. The bulk calculations show that WC is a semimetal with a low density-of-states (DOS) at E sub F and a Fermi surface consisting of several small electron and hole pockets. According to the surface studies, both the W(1 x 1) and C(1 x 1) faces exhibit distinctive surface-state features and an enhanced surface DOS near E sub F . The calculated work function for the tungsten surface, phi (W) = 5.2 eV, is 1.2 eV smaller than that for carbon. Additional differences between the two surfaces are reflected in the corrugation amplitudes of the charge density in the vacuum region. These features will be useful for establishing the surface composition in experimental studies on WC(0001) samples. 32 ref.--AA