This grant from the Theoretical and Computational Chemistry Program supports development of new methods for obtaining approximate solutions to the mathematical equations governing molecular electronic structure and the application of such techniques to a variety of important prototype chemical problems. Method development will focus on analytic calculation of derivatives for correlated wavefunctions, allowing for more complete characterization of potential energy surfaces. Applications will include studies of the structure and dynamics of conformers of 1,3 butadiene, the equilibrium geometry of the ammonia dimer, and reaction pathways for the formation of diketene and two closely related isomers. These studies will improve our qualitative understanding of how chemical reactions occur.