Acetylene on Si(111) from computer simulations

The interaction between the acetylene molecule (C_2H_2) and the Si(111)-(7 x 7) surface is studied with the combined use of ab initio and empirical methods. Several possible chemisorption configurations are explored, which may be helpful to rationalize recent experimental results. The kinetics of the chemisorption process can be described by identifying the low-energy paths between pairs of stable configurations. This can be done by means of accurate ab initio calculations only for small-scale models of surface reconstructions. It is shown that large-scale calculations based on the use of semi-empirical potentials, validated by ab initio calculations for small-scale models, can be an efficient tool to study chemisorption reactions of molecules occurring on complex semiconductor surfaces.