Quantum Chemistry Provides Potential Energy Surface

QUANTUM CHEMISTRY PROVIDES POTENTIAL ENERGY SURFACE 

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QUANTUM CHEMISTRY PROVIDES POTENTIAL ENERGY SURFACE... 

Probably even more important to computational quantum chemistry is the development in the analytical evaluation of first, second and higher derivatives of the potential energy with respect to nuclear coordinates . These analytical derivative methods are indispensable to the location and characterization of the stationary points (minima or transition states) on the potential energy surface and have greatly advanced the scope of applicability of ab initio calculations. Ab initio calculations are in a position to predict many new types of the heavier group 15 compounds and provide valuable information for the interpretation of complex experimental data. 

It is hoped that this section provides a useful introduction to ab initio studies of excited states. In this challenging area in quantum chemistry, it is not always straightforward to compare results of such calculations with experimental values because information about molecular excited states (and, in particular, the associated potential energy surfaces) is very scarce. Indeed, while the prediaion of infrared spectra has clearly been the most fruitful area of application for quantum chemical methods in the past decade, it is likely that theoretical studies of electronically excited states will continue to grow in importance. In particular, the availability of accurate (and therefore predictive) methods such as the EOM-CCSD approach in programs such as ACES II will serve to make accurate calculations of these systems accessible to a wide range of users. 

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