Abstract
The first principle Korringa-Kohn-Rostoker functional and basis functions are transformed directly into the hybrid nearly-free-electron tight binding (H-NFE-TB) form for the case of the transition metals in which the valence electrons behave like virtual bound states or resonances. It is shown that the resulting basis functions are indeed consistent with the NFE-TB picture, because the TB Bloch sums are rapidly convergent over the first few nearest neighbours since the oscillating tails of the resonant wavefunctions have been completely taken care of by the conduction basis set. Further, the H-NFE-TB matrix elements are accurate to second order in the width of the d band and, therefore, contain terms that are directly equivalent to the orthogonality and three-centre integrals of the conventional TB scheme. Finally, the basis functions are orthonormalized and the corresponding energy independent model Hamiltonian presented. The accuracy of this H-NFE-TB representation is illustrated by comparison with the first principle wavefunctions and band structure of iron.