  The ground state band structure, magnetic moments, charges and population
numbers of electronic shells of Cu and Fe atoms have been calculated for
chalcopyrite CuFeS2 using density functional theory. The comparison between our
calculation results and experimental data (X-ray photoemission, X-ray
absorption and neutron diffraction spectroscopy) has been made. Our
calculations predict a formal oxidation state for chalcopyrite as
Cu$^{1+}$Fe$^{3+}$S$_{2}$$^{2-}$. However, the assignment of formal valence
state to transition metal atoms appears to be oversimplified. It is anticipated
that the valence state can be confirmed experimentally by nuclear magnetic and
nuclear quadrupole resonance and M\"ossbauer spectroscopy methods.
