The Potential Energy Surface PES Concept

The PES is one of the most important issues of theoretical chemistry. One reason consists in the validity of the Born-Oppenheimer approximation (1927) for systems in the ground state. This seems to be confirmed by experience which has been gathered until now. The Born-Oppenheimer approximation makes the molecular structure to the central dogma of molecular science. Considering the molecular structure controversy, we feel that a possible revolution in the understanding of chemical structure will be based on an extensive check of the Born-Oppenheimer approximation and the quantum mechanical theory used in general at this time. Modern PES analyses in particular show that isopotential or quasi-isopotential energy domains, which in a 

The Born-Oppenheimer approximation decouples the electronic motion from that of the nuclei thus allowing to determine the potential energy for any atomic configuration (we refer to the textbooks and mention especially some new publications ). In other words, a global PES provides the potential energy as a function of the nuclear geometry of the system. For N atoms the potential energy 

It should be added that in quantum chemistry the zero of the potential energy is defined by the isolated electrons and bare nuclei. Thus, the so-called total energy can be represented in terms of the electronic energy E and the nuclear repulsion energy E  

It is evident that the total energy by definition includes the very large and predominant part of the energy due to the inner-shell electrons which are primarily not responsible for chemical bonding. However, the reference point of the potential energy may be shifted towards the energy of isolated reactants (or any other particular atomic arrangement)  

In empirical PES calculations of interacting molecular species the energy appears directly in this form. 

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Guidelines in the Developnent of tic Theory of Chemical Reactivity Using the Potential Energy Surface (PES) Concept... 

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