Core Potentials

In the standard approach the Coulomb potential and the charge density due to the atomic frozen core are computed from the frozen one-electron orbitals. adf stores the computed core density and core potential for each atom type in the molecule on a file TAPE12. Alternatively, you may attach a file with (core) potentials and densities. The file must have the same structure as the standard TAPE12. It should contain one or more sections, each with the core information for one type of atom. With the key corepotentials you specify the core file and (optionally) which sections pertain to the distinct atom types in the molecule. It is a general key that can be used as a simple key or as a block key.

COREPOTENTIALS corefile { &
  atomtype index
  atomtype index
  ...
end}

corefile

The file with core potentials and charge densities. The name may contain a path.

atomtype

One of the atom type names as defined by atoms.

index

Points to the core section on the attached file that applies to the atom type. Different atom types may use the same section. A non-positive index tells the program that the atoms of that type don't have a frozen core. If the information on the corresponding fragment file (or data file in Create mode) indicates the contrary the program will abort with an error message.

If the key is used as a simple key (specifying only the core file) the sections on the file are associated with the atom types in order: the first section is used for the first atom type, et cetera. This is overruled by applying the block form. However, since the key must have the core file as argument, the block form requires that you apply the continuation symbol: an ampersand (&), separated from the core file name by at least one blank.

If you omit an atom type from the data block it gets a zero index (no core).

The attached file may contain more sections than used in the calculation, and the indices specified in the data block don't have to be in ascending order, consecutive, or cover a specific interval.

When a file with non-standard (e.g. relativistic) cores is attached and used in the calculation of an atom or molecule, and the result is used as fragment in a subsequent calculation, you should attach and use the same core potentials again. Otherwise, the program will internally compute the standard core potentials and hence implicitly employ another fragment than you may think, i.e. a fragment with other properties. adf will not check anything in this respect and corepotentials should therefore be handled with great care.

The primary application of the corepotentials option is to include (scalar) relativistic corrections in the (frozen core part of the) Fock operator. The relativistic core potentials can be computed with the auxiliary program dirac (see the utilities document)