Ab initio calculation of interstitial-atom effects in YFe10Mo2X (X=E,H,B,C,N,O,F)

Neutron diffraction was used to determine the crystallographic structures of the YFe{sub 10}Mo{sub 2} and YFe{sub 10}Mo{sub 2}X (X=H,N). The spin-polarized muffin-tin-orbital method was applied to calculate the electronic structures of YFe{sub 10}Mo{sub 2}X (X=H,B,C,N,O,F) and YFe{sub 10}Mo{sub 2}E, which is YFe{sub 10}Mo{sub 2} with an empty sphere insertion. Both N and H atoms were found to reside on the interstitial 2b sites. The magnetovolume effect and chemical bonding effect of interstitial X atoms are investigated by a systematic analysis of the local magnetic moments {mu}{sub loc}, Fermi-contact hyperfine fields (H{sub FC}), and isomer shifts (IS) at different Fe sites in YFe{sub 10}Mo{sub 2}X (X=H,B,C,N,O,F) and YFe{sub 10}Mo{sub 2}E. It is found that the insertion of the X atom changes not only Fe-Fe interaction, but also Fe-X interaction, and the latter is dependent on the chemical properties of X atoms. It can be concluded that, based on our results, the chemical bonding effect in R{minus}(Fe,M){sub 12}{minus}X is determined by the features of the Fe-X bonds. The role of the X atom is not only to increase the magnetic moments and hyperfine fields through magnetovolume effects, but also to affect those by chemical-bonding effects. The chemical-bonding effect is strongly dependent onmore » the X atom. {copyright} {ital 1997} {ital The American Physical Society}« less