Modified XB potential for simulating interactions of organic molecules with Si surfaces

We have evaluated the performance of the popular ``eXtended'' Brenner (XB) empirical potential in numerical simulation of the interaction of organic molecules with the Si(100) surface. Some limitations and failures, due to the original choice of the potential parameters, are discussed. We propose an improved parametrization which is able to circumvent most of these shortcomings. The advantages of this modified XB potential are shown by investigating the adsorption of organic molecules on Si(100), both in the case where the process leaves the molecule intact (acetylene, benzene, 1,4-cyclohexadiene) and in the case where the molecule dissociates upon adsorption (methylsilane).