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Bonding in an unusual nickel carbide

机译:粘结不寻常的碳化镍

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The bonding in an unusual nickel carbide polymer network synthesized by Musanke and Jeitschko is analyzed using qualitative, band-structure calculations in the framework of extended Huckel tight-binding theory. The carbide features infinite, one-dimensional, vertex-sharing chains of Ni squares. Each square is centered by a carbon and flanked by C-2 units. In this electron-rich polymer, the Ni atoms act as electron accepters through their s and p orbitals. The orbital interaction schemes reveal that there is little Ni-Ni bonding and essentially no Ni to C-2 back-donation. Molecular orbital interaction diagrams of some molecular models art: used to describe the bonding in (1)(infinity)[Ni3Cs5](8-). We also discuss the stability of the planar building block of the polymer, (CNi4)(4-) (which resembles planar CH4) with respect to a "tetrahedral" alternative and we do so for the extended (1)(infinity)[Ni3C](4-) and (1)(infinity)[Ni3C5](8-) chains. In each model case the tetrahedral alternative is favored, and there is no sign of stabilization of a crucial CL4 orbital. Such stabilization is partially achieved through bonding to two Ca axial to the C in the center of the Ni-4 ring, but it takes the entire inter-chain calcium network to effect the observed stabilization. [References: 52]
机译:在扩展的Huckel紧密结合理论的框架内,使用定性的能带结构计算方法分析了Musanke和Jeitschko合成的不寻常的碳化镍聚合物网络中的键。碳化物具有无限的一维Ni正方形的顶点共享链。每个方块均以碳为中心,两侧为C-2单元。在这种富含电子的聚合物中,Ni原子通过其s和p轨道充当电子受体。轨道相互作用方案表明几乎没有Ni-Ni键合,并且基本上没有Ni到C-2的背向供体。一些分子模型领域的分子轨道相互作用图:用于描述(1)(无穷大)[Ni3Cs5](8-)中的键合。我们还讨论了聚合物的平面结构单元(CNi4)(4-)(类似于平面CH4)相对于“四面体”替代方案的稳定性,我们针对扩展的(1)(无穷大)[Ni3C ](4-)和(1)(无限)[Ni3C5](8-)链。在每种模型情况下,都倾向于使用四面体替代方案,而且没有关键CL4轨道稳定的迹象。这种稳定化是通过在Ni-4环的中心与C轴向上的两个Ca结合而实现的,但是它需要整个链间钙网络来实现观察到的稳定化。 [参考:52]

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