Theory for the(1×1)Rumpled Relaxations at TiC(001) and TaC(001) Surfaces

Abstract

A simple $d-p$ tight binding model is proposed for the transition metal monocarbides. We show that it reproduces the observed crystal structures and (100) surface relaxations. In particular, the model demonstrates that the reversal in the surface relaxations between TiC(100) and TaC(100) is driven by the $d-p$ band filling, and that the reversal requires the $d-d$ interactions between second neighbor metal atoms.