The procedure for geometry optimization is also a pRocedure for energy minimization. This is typically an iterative procedure since the energy is surface is multi-dimensional. The procedure involves three robust methods, which can be used in differing ways depending on the implementation in the particular code. The goal is to find a global minimum. However, often one must settle for a local minimum since the global minimum may be far away from the starting structure. The reason that geometry optimization is in the present lecture is that it is essential to find a minimum in conformational space in order to be able to calculate vibrational frequencies. Calculating frequencies prior to finding a proper minimum in the geometry space will lead to potential artifacts.
