Molecular Interactions with Many-Body Methods.

Modern military technology has become highly dependent on a detailed knowledge of atom-molecule and molecule-molecule interactions. This type of information is required in diverse defense applications including chemical laser development, in the detection and modeling of plumes, and in the decomposition of energetic materials. The description of forces governing molecular reactions is provided by potential energy surfaces. These surfaces are the crucial first step in dynamics calculations that provide required information about state-to-state cross-sections and rate constants. Since potential energy surfaces are not generally available from experiment, the most reliable approach to their determination lies in the development and application of predictive ab initio quantum mechanical methods. The following annual report describes our research on the development of many-body perturbation theory MBPT and related infinite-order coupled-cluster CC methods for potential energy surfaces.