应用量子化学研究Ca_2Fe_（2-x）Al_xO_5的水化活性

用量子化学ＳＣＣ—ＤＶ—Ｘａ方法分析了Ｃａ_２Ｆｅ_（２-ｘ）ＡｌｘＯ_５体系中的Ｃａ_２Ｆｅ_２Ｏ_５（即Ｃ_２Ｆ），Ｃａ_２Ｆｅ_（１．４３）Ａｌ_（０．５７）Ｏ_５和Ｃａ_２Ｆｅ_（１．２８）Ａｌ_（０．７２）Ｏ５．认为它们的水化活性随Ａｌ的增加而提高的原因是：（１）Ａｌ的净电荷比Ｆｅ高，易吸收水分子的孤对电子；（２）Ａｌ-Ｏ键比Ｆｅ-Ｏ键弱，易断裂而容易与水反应．

ON THE HYDRATION ACTIVITY OF Ca_2Fe_(2-x)Al_xO_5 WITH COMPUTATIONAL QUANTUM CHEMISTRY

In this paper,Ca2 Fe2 O5 (C2 F), Ca2Fe1.43 Al o.57 O5 and Ca2Fe1.28 Al0.72O5 in Ca2Fe(2-x) AlxO5system are investigated with a new SCC-DV-Xa method.The computational models are octahedron and tetrahedron.Through computation with a CYBER-930 computer,following results are obtained:(1)the Fermi energy of octahedron and tetrahedron in Ca2Fe2O5 are -9.76 and -2.34eV respectively,in Ca2Fe1.43 Al0.57 O5 are -10.65 and -3.40eV,and in Ca2Fe1.28 Al0.72 O5 are -11.54 and -3.47eV respectively.(2)the net charge of octahedron and tetrahedron of Fe in Ca2Fe2O5 are 0.5895 and 0.2186,that of Al in Ca2Fe1.43Al0.57O5 are 0.8573 and 0.4319,and that of Al in Ca2Fe1.28 Al0.72O5 are 1.0302 and 0.5027.(3)the average covalent bond order of Fe-O bond of octahedron and tetrahedron in Ca2Fe2O5 are 0.4187 and 0.6209,of Al-O bond in Ca2Fe1.43Al0.57O5 are 0.3594 and 0.4936,and of Al-O bond in Ca2Fe1.28 Al0.72O5are 0.3448 and 0.4950 respectively. From all of the above,it is considered that the reason of hydration activity increasing with the adding of Al content is(1)it is easy to absorb the solitary electron pair of water to react with water because the net charge of Al is higher than that of Fe; and (2) the bonds can be broken easily to lead to hydration reaction because the covalent bond of Al-O is weaker than that of Fe-O.