What is the basic idea behind the basis set utilities?

The basis set utilities generate ADF atomicdata files for ET basis and fit sets, using some simple input from the user. With the first utility, the user selects the ET basis set for the occupied shells that should form the starting point. These were developed and tested on atomic total and orbital energies by Prof. Del Chong during a sabbatical spent in Amsterdam. These basis sets are intended to be at least of the quality of basis V, but usually better. However, also some smaller ET basis sets were made for more economical calculations. After selecting the basis set for the occupied shell, the user has to specify whether additional polarization, diffuse, or contracted basis functions should be added (also tight functions for ZORA calculations can be added, but this has not been properly tested). To answer these questions requires of course some expertise in basis sets. It is therefore recommended for users with some experience in this area. However, suitable, safe defaults are defined and suggested in the scripts. The user also defines the quality of the fit set which is desired. Only the highest quality fit set has been thoroughly tested. The other options are not supported at the moment. We will now describe the input and output of the various utilities in some detail.