- Used for solving Schrodinger’s Equation for molecules.
- Because electrons are so much light and their resulting motion so mfaster than that of the nuclei
- Quantum mechanical computations for the electron wave functions can assume that the nuclei are essentially fixed in space, compared to the electrons.
- It is then possible to compute the electronic states for a given set of ffixed nuclear positions.
- This computations is then done many times, once for every set of nuclear positions.
- Energy vs positions give the potential energy surface, from which the nuclear motion can be computed.
- This is separation of variables, but still an approximation because the variables being separated are linked.