  We present a detailed derivation of the Gutzwiller Density Functional Theory
that covers all conceivable cases of symmetries and Gutzwiller wave functions.
The method is used in a study of ferromagnetic nickel where we calculate ground
state properties (lattice constant, bulk modulus, spin magnetic moment) and the
quasi-particle band structure. Our method resolves most shortcomings of an
ordinary Density Functional calculation on nickel. However, the quality of the
results strongly depends on the particular choice of the double-counting
correction. This constitutes a serious problem for all methods that attempt to
merge Density Functional Theory with correlated-electron approaches based on
Hubbard-type local interactions.
