Let'egin by discussing what the discipline of theoretical chemistry is about. I think most young students of chemistry think that theory deals with using puters to model or simulate molecular behaviors. This is only partly true. Theory indeed contains under itroad umbrella the field of putational simulations,and it is such applications of theory that have gained much recent attention especially as powerful puters and user-friendly software packages have bee widely available. However, this discipline also involves analytical theory, which deals with how the fundamental equations used to perform the simulations are derived from the Schrrdinger equation or from classical mechanics, among other things. The discipline also has to do with obtaining the equations that relate laboratory data (e.g., spectra, heat capacities, reaction cross-sections) to molecular properties(e.g., geometries, bond energies, activation energies). This analytical side ofthe0ry is also where the equations of statistical mechanics that
