Cluster study of the dimer geometry on the C(100) surface

Recently, we have shown that the energetics and structures of dimers on the Si(100) surface can be quite accurately obtained using cluster calculations. Our results show reasonable agreement with recent first-principles slab calculations and suggest that previous cluster calculations predicted an unbuckled dimer structure because of the use of inappropriate geometry constraints in the optimization. Here we extend this study to the C(100) surface. We find an unbuckled dimer geometry for this surface and show that dimer buckling does not occur because the increase in the potential energy with buckling is dominant over the decrease in the kinetic energy. (C) 1998 Elsevier Science B.V. All rights reserved.