利用离散变分Xa法计算了单晶Ni_3Al的一个原子簇(Ni_(15)Al_(12)),并据此分析了能级结构、电子态密度,计算了Ni_3Al中原子间的键级及相应的组成。键组成分析证明:Ni-Al键与Ni-Ni键具有较好的相似性,p-d键在两种键的组成中都占有较大比例。Ni_3Al的Ll_2结构,使两种相似的键在空间呈均匀分布,宏观上Ni_3Al表现出较高的强度。单晶体良好的韧性归因于Ni-Al键与Ni-Ni键的相似性,方向性较强的共价键在晶界处受到削弱导致多晶体的本征脆性。
A cluster of monocrystalline Ni_3Al has been studied by the discrete variationalXα(DV-Xα) method. From the computation, the energy level structures and the densities ofelectronic states were investigated. The bond order between the constituent atoms and theircomponents have been calculated. The analysis of bond component shows that the Ni-Nibond is very similar to the Ni-Al bond. The Ll_2 structure of Ni_3Al leads these similar bondsto disperse evenly in the space. In macroscopical properties, Ni_3Al exhibits high strength. Theductility of monocrystal is due to the similarity of Ni-Ni bond to Ni-Al bond. The brittlenessof polycrystal is attributed to the weakening of directional covalent bonding at grain bounda-ry.
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