Bulk and surface electronic structure of hexagonal WC

The bulk and surface electronic structure of hexagonal WC have been investigated by means of self-consistent scalar relativistic calculations that apply the linear augmented-plane-wave method. The surface studies consider WC(0001)-W(1×1) and -C(1×1) faces and assume a slab geometry with bulk interlayer spacings. Separate calculations have been carried out for symmetrical ninelayer slabs containing either W(1×1) or C(1×1) 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 $E_F$ and a Fermi surface consisting of several small electron and hole pockets. According to the surface studies, both the W(1×1) and C(1×1) faces exhibit distinctive surface-state features and an enhanced surface DOS near $E_F$. The calculated work function for the W surface, $\phi \left(\mathrm{W}\right)=5.2\mathrm{}$ eV, is 1.2 eV smaller than that for C. 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.