Reconstruction of small Si cluster after ethylene adsorption: A full-potential linear-muffin-tin-orbital molecular-dynamics study

Using full-potential linear-muffin-tin-orbital method, we have performed mo lecular-dynamics simulations for the ethylene adsorption on the Si5-7-clust er surfaces. The calculations show that the most favored adsorption site is the short bridge site for Si-5 cluster, with the adsorption energy 1.78 eV . The adsorption structure of ethylene molecule is similar to that of the d imer-maintained structure for C2H4+Si(100)-(2x1). It indicates that ethylen e is di-sigma bonded to the Si-5 cluster. At the same time, the Si-5 cluste r reconstructs after ethylene adsorption. The three-center bond among side atoms breaks, and new bonds form. For Si-6 cluster, the most favored adsorp tion site is the atop site on the side atom. After adsorption, Si-6 cluster reconstructs from tetragonal bipyramid to edge-capped trigonal bipyramid. The short bridge is the only available site to adsorb ethylene for Si-7 clu ster. (C) 1999 American Institute of Physics. [S0021-9606(99)51720-0].