Just another WordPress site - Ruhr-Universität Bochum

Interatomic potentials for modelling the vapour phase growth of semiconductor thin films must be able to describe the breaking and making of covalent bonds in an efficient format so that molecular dynamics simulations of thousands or millions of atoms may be performed. We review the derivation of such potentials, focusing upon the emerging role of the bond-based analytic bond-order potential (BOP). The BOP is derived through systematic coarse graining from the electronic to the atomistic modelling hierarchies. In a first step, the density functional theory (I)FT) electronic structure is simplified by introducing the tight-binding (TB) bond model whose parameters are determined directly from DFT results. In a second step, the electronic structure of the TB model is coarse grained through atom-centered moments and bond-centered interference paths, thereby deriving the analytic form of the interatomic BOP. The resultant σ and π bond orders quantify the concept of single, double, triple and conjugate bonds in hydrocarbon systems and lead to a good treatment of radical formation. We show that the analytic BOP is able to predict accurately structural energy differences in quantitative agreement with TB calculations. The current development of these potentials for simulating the growth of Si and GaAs thin films is discussed. (C) 2006 Elsevier Ltd. All rights reserved.