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

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 thesporbital hybridization of carbon. It is proposed that, at the initial stage, C sinks into the hollow site and bonds to one Ni atom underneath. TheC-1polarizes and pushes its surface neighbors radially away from the site center, and hence aNi5Ccluster forms. Then,sphybridization of the C happens, leading to aNi4Ctetrahedron. Besides theNi+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 beNi+ions and the other half to beNi2+ions. As a result, one-dimensional nonuniform "- (+) - (2+) – (2+) - (+) – (+) -" chains form along the direction. It is suggested that the forces arising from charge redistribution drive the reconstruction. Calculation reveals that an increase of~ 90dyne electrostatic repulsion along the direction and a responding~ 130dyne bond compression stabilize the network of (2× 2)p4g clock rotation.