Quasiparticle band structure of Ni andNiSi2

Expressions for the hole self-energies of a metal with hybridized sp and d bands have been obtained using the low-density t-matrix approximation and a Hubbard Hamiltonian to treat correlation effects. The theory provides a significant improvement with respect to previous calculations based on the Hubbard Hamiltonian, since it takes into account the details of the single-particle band structure in the calculations of the two-hole propagator and uses a self-consistent approach for the evaluation of self-energy corrections. The theory is applied to the evaluation of the quasiparticle density of states and dispersion for Ni and ${\mathrm{NiSi}}_2$. The results allow elucidation of the role of many-band and hybridization effects in determining the self-energy behavior.