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 structu res of the YFe10Mo2 and YFe10Mo2X (X=H,N). The spin-polarized muffin-t in-orbital method was applied to calculate the electronic structures o f YFe10Mo2X (X=H,B,C,N,O,F) and YFe10Mo2E, which is YFe10Mo2 with an e mpty sphere insertion. Both N and H atoms were found to reside on the interstitial 2b sites. The magnetovolume effect and chemical bonding e ffect of interstitial X atoms are investigated by a systematic analysi s of the local magnetic moments mu(loc), Fermi-contact hyperfine field s (H-FC), and isomer shifts (IS) at different Fe sites in YFe10Mo2X (X =H,B,C,N,O,F) and YFe10Mo2E. It is found that the insertion of the X a tom 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-(Fe,M)(12)-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 h yperfine fields through magnetovolume effects, but also to affect thos e by chemical-bonding effects. The chemical-bonding effect is strongly dependent on the X atom.