Ab initio density functional studies of stepped TaC surfaces

We report on density-functional total-energy calculations of the step formation and interaction energies for vicinal TaC~001! surfaces. Our calculations show that doubleand triple-height steps are favored over singleheight steps for a given vicinal orientation, which is in agreement with recent experimental observations. We provide a description of steps in terms of atomic displacements and charge localization and predict an experimentally observable rumpled structure of the step edges, where the Ta atoms undergo larger displacements compared to the C atoms.