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Core expansion functions
This part has the form
CORE ns, np, nd, nf
1s 7.68
...
(etc.)
...
end
It looks very much like the basis
functions: a list of Slater type function descriptions, closed
by end. The header
record however (core...) contains in
addition four integers ns, np, nd, nf. They are the numbers respectively of s-, p-,
d-, and f- frozen core shells in the atom. If you create for
instance a Ruthenium atom with a frozen core up to the 4p shell, these numbers
would be 4 3 1 0 : four frozen s-shells (1s,2s,3s,4s), three frozen p-shells (2p,3p,4p), one frozen d-shell (3d), and no frozen f-shells.
The core expansion sets defined in this
section are used to describe the frozen core orbitals; they are not
included in the valence basis set. In the list of core expansion sets all s-type functions must come first, then the p-type functions, then the d-functions, and then the f-functions (as far as applicable).
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