An optimization method for large van der Waals system

An optimization method for the geometry of large van der Waals system was suggested by discussing parallel dimer of benzene. The key of this method is to place some basis functions at interaction region of van der Waals molecules. It is possible to optimize large supramolecular system by using this method because it can greatly decrease the number of basis sets. This method was used to optimize the geometry of dimer of pyrene and the result is satisfactory.