In this project in the Theoretical and Computational Program of the Chemistry Division, Professor Schlegel will develop new algorithms for reaction path following on molecular potential energy surfaces. The PI uses these computational tools to study the thermodynamics and reactivity of molecules containing silicon, hydrogen and flourine that are relevant to chemical vapor deposition of amorphous silicon films for photovoltaics and etching of silicon surfaces for microelectronics. A family of five new reaction path following algorithms is proposed. Previously developed spin projection methods for correlation corrections to ground state wave functions will be extended and spin projections will be developed for CI singles calculations (single substitutions in the ground state determinantal function) of excited states. A new transition structure optimization algorithm and a new type of electric field dependent basis to calculate improved dipole moments, polarizability and infrared intensities will be developed. In the area of applications the mechanism of simple photochemical reactions will be explored. Reaction path following will be used to study the effect of solvent molecules on transition states for SN2 reactions. Transition structures and barrier heights will be determined for radical abstractions, radical additions to multiple bonds and diradical cycloaddition reactions. The study of the thermal decomposition of silicon compounds will be continued.
