In a comparative study we calculated the spin and orbital moments, spin and charge densities, and 4f crystal field (CF) parameters of the rare-earth transition-metal intermetallics ${\mathrm{Sm}}_2$${\mathrm{Fe}}_{17}$, ${\mathrm{Sm}}_2$${\mathrm{Fe}}_{17}$${\mathit{Z}}_3$ (Z=C,N), and ${\mathrm{Sm}}_2$${\mathrm{Co}}_{17}$ using a relativistic optimized linear combination of atomic orbitals method. The itinerant valence electron states were treated in the local-spin-density approximation (LSDA), whereas the localized 4f states were described as open core states within the self-interaction-corrected LSDA. The calculations yield magnetic moments in good agreement with experiment. While all local moments of ${\mathrm{Sm}}_2$${\mathrm{Fe}}_{17}$ increase upon lattice expansion, the moments of atoms neighboring the interstitial sites decrease and those of more distant Fe atoms increase upon insertion of interstitial N or C. In N interstitial atoms all ${2\mathrm{p}}_{\mathrm{\alpha }}$ orbitals are polarized antiparallel to their respective Fe and Sm neighbor atoms in the bond direction, whereas in C all ${2\mathrm{p}}_{\mathrm{\alpha }}$ orbitals are polarized antiparallel to the Fe atoms neighboring the interstitial site. The second-order CF parameters ${\mathit{A}}_2^0$ dominating the rare-earth magnetocrystalline anisotropy are found to have the same sign and order of magnitude as those derived from magnetization data. In accordance with experiment the calculated negative ${\mathit{A}}_2^0$ is larger for the Co compound than for the Fe parent compound and is strongly increased upon insertion of interstitial N or C. The agreement between theory and experiment is improved by taking into account the CF contribution arising from the asphericity of the exchange-correlation potential of the non-4f states. © 1996 The American Physical Society.

• Received 14 November 1995

DOI:https://doi.org/10.1103/PhysRevB.53.7111