The fixed-core Hartree-Fock approximation

The above derivation has assumed that the solution is stationary with respect to all allowed variations. In practice, it may be convenient to assume that certain radial functions are ``fixed'' or ``frozen'': in other words, these radial functions are assumed to be given. Such approximations are often made about core orbitals and so, this is called a fixed-core HF approximation. Of course, the system of equations defining the solution includes only equations for radial functions that vary.

2001-01-09