  We have developed the crystal-field approach with strong electron
correlations, extended to the Quantum Atomistic Solid-State theory (QUASST), as
a physically relevant theoretical model for the description of electronic and
magnetic properties of 3d-atom compounds. Its applicability has been
illustrated for LaCoO3, FeBr2 and Na2V3O7. According to the QUASST theory in
compounds containing open 3d-/4f-/5f-shell atoms the discrete atomic-like
low-energy electronic structure survives also when the 3d atom becomes the full
part of a solid matter. This low-energy atomic-like electronic structure, being
determined by local crystal-field interactions and the intra-atomic spin-orbit
coupling, predominantly determines electronic and magnetic properties of the
whole compound.
  We understand our theoretical research as a continuation of the Van Vleck's
studies on the localized magnetism. We point out, however, the importance of
the orbital magnetism and the intra-atomic spin-orbit coupling for the
physically adequate description of real 3d-ion compounds and 3d magnetism. Our
studies clearly indicate that it is the highest time to ''unquench'' the
orbital moment in solid-state physics in description of 3d-atom containing
compounds.
  PACS No: 75.10.D; 71.70.E
  Keywords: magnetism, transition-metal compounds, 3d magnetism, crystal field,
spin-orbit coupling, orbital magnetism
