H₂-induced environmental embrittlement in ordered and disordered Ni₃Fe : An electronic structure approach

The different behaviors in H₂-induced environmental embrittlement in ordered and disordered Ni₃Fe are associated with differences in their electronic structures. The experimental study on electronic structures of ordered and disordered Ni₃Fe has been carried out by electron energy-loss spectroscopy (EELS). The onset energy of Ni L_2,3 edges from ordered phase is 0.3 eV lower than that from disordered phase, while the 3d occupancy of Ni atoms in ordered phase is 0.07 electrons/atom less than that in disordered phase. Severe H₂-induced environmental embrittlement in ordered phase is attributed to rather negative dissociative adsorption energy of hydrogen at surfaces, which arises from upward shifting of the valence band center of Ni. © 2006 Elsevier Ltd. All rights reserved.