In this project in the Theortetical and Computational PhysicalChemistry Program of the Chemistry Division, Prof. Berry will calculate the behavior of few-body systems at the atomic level. The work will examine vibration-rotation states of small molecules and freezing and melting in clusters of molecules. Electron correlation in atoms, especially the determination of the best approximate quantum numbers for particular states, will be quantified. The dynamics of highly excited rotation- vibration states will be used to predict spectra involving large amplitude motion and nonrigid behavior. Analysis of how chaos and ergodicity develop as functions of energy will be examined during solid-liquid phase changes in small clusters.