With this grant in the Theoretical and Computational Chemistry Program of the Chemistry Division, Professor Hall will use ab initio full-gradient geometry optimization techniques, including multiconfiguration self-consistent-field and configuration interaction methods to solve problems of current interest in inorganic and organometallic chemistry. He will continue methods development in three areas. To improve the time to solution on multiprocessing computers, he will continue working on parallel code of which the gradient section is now complete. In order to handle large numbers of electrons and orbitals, he will implement a modification of the complete active space multiconfiguration self-consistent-field technique. Lastly, he will continue the use of and improve the understanding of the topological method of analysis due to Bader. The systems to be studied are related to three fundamental steps in catalysis: oxidative-addition, substitution, and migratory-insertion. Specifically, he will examine several important questions about the nature of the C-H activation. The methods to be utilized will allow him to draw conclusions about a group of closely related molecules with modest basis sets and a moderate degree of electron correlation. %%% Professor Hall will perform theoretical compuations that will aid in understanding the elementary steps in a number of chemical reactions that are important in catalytic processes.