For some specific appliacations the wfn file must be modified because GAUSSIAN contains a bug in the case of ROHF calculations (all the orbitals are doubly occupied!). There are two wfn manipulations:
Molecular ab initio programs use basis real functions, in the case of linear molecules these computed MOs are not eigenfunctions of the Lz operator and therefore the cylindrical symmetry can be lost. This is particularly the case for open shell systems in a Π state. sym_wfn as been wriiten to correct this drawback for 2Π states calculated with ROHF. In order to get symmetrized figures run sym_wfn before performing the grid09 calculation. The program prompts the user to get the input wfn file name and the name of the symmetrized sym_wfn file.
For large molecular systems mod_wfn enables to restrict the analysis to a subpart of the system. The atoms of the subpart of interest and their first neighbours are entered as data of mod_wfn
The selected subpart is the functional group. The atoms in the wfn appear in the following order:
The selected atoms are C(2), C(4), O(5), O(6) and H(11). The input is :