Electronic structure and FIM imaging mechanism of Fe-Al intermetallic compounds

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Electronic structure and FIM imaging mechanism of Fe?Al intermetallic compounds

The electronic structure and some one-electron properties of binary intermetallic compounds Fe₃Al (the F₁∶Al₄ model cluster) and FeAl (the Fe₇Al₈ and Fe₄Al₄ model clusters) are investigated by the SCF-X_α-SW method. The results show that the binding tendency between an Fe atom and the Fe₃Al cluster is a little weaker than that between an Al atom and the Fe₃Al cluster, which is in contrast to the case in FeAl. And charge is transferred from Al atoms to Fe atoms in both systems. Thus it is concluded that Al atoms contribute to the FIM image of Fe₃Al whatever the imaging mechanism, selective evaporation or selective ionization is, which is in good agreement with our FIM experimental results. For FeAl, no definite experimental evidence regarding FIM imaging atom species is available so far. But our calculated result that Al atoms will be evaporated preferentially leads to the prediction that Fe atoms will be imaged in FIM micrographs. Project supported by the National Natural Science Foundation of China (Grant No. 59771018).