Abstract: Based on the feature of crystal sites occupied by alloying elements,a model cluster,investi- gating the interaction mechanisms of nonmagnetic element Cu in RECo_5 type alloy,has been presented.The electronic structure has been calculated with SCF-X_a-SW method.The calcu- lating results show that,after Cu replaced 2c crystal site Co,the energy spectrum of the mod- el cluster will move towards a shallow trap po.tential,the energy gap becomes small,the charge among the atoms will redistribute,and some new states to which impurity contributes will pro- duce.Partial-wave local density of states gives the interaction between atoms.Results of Hellmman-Feynman force show that the thermal expansion anisotropy of the model cluster decreases considerably after Cu substitutes for 2c crystal site Co.

Key words: intermetallic compound, electronic structure