Basis functions

A list of Slater type basis function characteristics. This part has the following format (example):

BASIS
  1s 5.4
  2s 1.24
  ...
  (etc.)
  ...
end

The words basis and end signal the beginning and the end of this section in the data file. The records in-between list the basis functions; each record contains the main quantum number, the angular quantum number, and the exponential decay factor for a set of Slater type basis functions. A function description 3d 2.5 for instance represents the functions reY, m=-2,...,2.

The order of specification of the basis functions is not free. First must come the Core Functions used for core-orthogonalization, see Chapter 1.2. The CFs must be in order: s-functions first, then p-functions, then d-functions, and finally f-functions (as far as applicable). In the valence basis set there must be exactly one core-orthogonalization function for each frozen core shell (1s, 2s, 2p, ...).

Here as well as in all other function definitions below, the unit of length, implicit in the exponential decay factor, is bohr (atomic units), irrespective of the unit of length used in input for geometric items such as atomic positions (see units).