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The characteristic of intermetallic compounds is that metal bond coexist withcovalent bond, and has the long-range ordered superlattice structure. Therefore, theintermetallic compounds has unique electrical, magnetic, optical, acoustic properties,electron emission properties, high temperature strength, catalytic properties,chemical stability thermal stability and so on. At the same time, the intermetalliccompounds of iron and aluminum contain Fe and Al two common metal elements,free or less with strategic alloy elements （such as Ni, Cr, etc.）, so the cost of rawmaterials is much lower than Ti-Al and Ni-Al intermetallic compounds，and as it hasthe long-range ordered superlattice structure, the corrosion resistance to sulfide isstronger than the latter, therefore, the intermetallic compounds of iron and aluminumare expected to have wide applications in the heating element, heat exchanger tube,furnace fastener, sintered porous gas metal filter, etc. But the brittleness at roomtemperature of intermetallic compounds greatly limits its application as a hightemperature structural materials. The study proved that the test environment has acrucial effect on the brittleness of FeAl intermetallic compounds. Further researchconcluded that the environmental brittleness of Fe-Al intermetallic compounds is dueto hydrogen embrittlement which caused by hydrogen atoms that produced by therole of environmental water vapor and Al atoms. However, the microscopicmechanism is unclear.In this paper, we used the generalized gradient approximation （GGA） method inthe density functional theory （DFT） to create a supercell model of FeAl and Fe3Aland calculated the electronic structure of FeAl and Fe3Al before and after the Hatoms doping. Calculation results showed that in the intermetallic compounds of ironand aluminum, sp hybrid orbital of Al atom had a strong directivity, whichparticipated in the formation of pd polarization key between Fe-Al, and caused the brittleness of the crystal. In the case of the doping concentration of the H atoms is1%-2%, H atoms is added to the system of Fe-Al, the state of Al atoms which nearthe H atoms have changed, more lattice electron changed to covalent electron inorder to bond with H atom, which maked the local metal properties decrease insidethe crystal. Since the H atoms participated in the bonding, the bond meridians whichhave obvious anisotropy formed in the crystals and be more easier to cleavage.
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