DRIVING FORCE AND BOND STRAIN FOR THE C–Ni(100) SURFACE REACTION

Abstract

It is shown that the atomic states, bonding dynamics, driving force and bond strain for the C–Ni(100) surface reaction can be consistently understood by considering the sp orbital hybridization of carbon. It is proposed that, at the initial stage, C sinks into the hollow site and bonds to one Ni atom underneath. The C -1 polarizes and pushes its surface neighbors radially away from the site center, and hence a Ni 5 C cluster forms. Then, sp hybridization of the C happens, leading to a Ni 4 C tetrahedron. Besides the Ni + underneath the C adsorbate, three of the four surface Ni neighbors donate electrons to the adsorbate. The half-monolayer coverage of C defines therefore half of the surface Ni atoms to be Ni + ions and the other half to be Ni 2+ ions. As a result, one-dimensional nonuniform "- (+) - (2+) – (2+) - (+) – (+) -" chains form along the < 11> direction. It is suggested that the forces arising from charge redistribution drive the reconstruction. Calculation reveals that an increase of ~ 90 dyne electrostatic repulsion along the < 11> direction and a responding ~ 130 dyne bond compression stabilize the network of (2× 2)p4g clock rotation.