Douglas Doren is supported by a grant from the Theoretical and Computational Chemistry Program to continue his research in the study of reactions on silicon surfaces. First principles solutions of the electronic Schrodinger equation are used to determine interatomic interactions in models for reactions on silicon surfaces. From calculated interactions in many atomic configurations, a global description of the potential energy is developed which is then subsequently used in classical and quantum calculations of reaction rates and dynamics. Applications to be studied include desorption and diffusion of hydrogen atoms, abstraction of chemisorbed hydrogen, and adsorption and decomposition of silane. The immediate objective of Doren's research is to develop reliable methods for calculating mechanisms and rates of reactions on silicon surfaces, and to apply them to several examples which are important in semiconductor device fabrication. A mechanistic understanding of silicon surface chemistry will be essential for developing new semiconductor technologies that require unprecedented control over the properties of these materials.