Carbides of group VA transition metals
Carbides of group VA transition metals
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VA族过渡金属碳化物
DOI：
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发表时间：
1995
期刊：
影响因子：
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通讯作者：
A. Cottrell
中科院分区：
文献类型：
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作者：
A. Cottrell
本文对VA族过渡金属碳化物在不同C含量和晶体结构下的结合能进行了估算。在立方结构MCx中，几个因素有助于在x < 1时提供最佳内聚力，即使在存在过量C的情况下也是如此。其中值得注意的是费米能级下降时，出现在C亚晶格中的空缺。当x很大时，非常接近的邻居之间的强C-C排斥阻止了六边形结构变得稳定，即使在这些电子浓度下，底层金属子晶格预计更倾向于hcp而不是fcc。在M2 C中，C-C排斥贡献充分减少，以允许六方结构出现。进一步减少这种排斥性的贡献，再加上静电能的变化的机会，提供了一个强大的趋势，在M2 C的C子晶格的排序，导致高的排序温度。MST/3031
Estimates are made of the cohesive energies of the group VA transition metal carbides for various C contents and crystal structures. In the cubic structure MCx, several factors help to provide optimal cohesion at x < 1, even in the presence of excess C. Notable among these is a drop in the Fermi level when vacancies appear in the C sublattice. A strong C–C repulsion between very close neighbours prevents the hexagonal structure becoming stable when x is large, even though the underlying metal sub lattice is expected to prefer hcp to fcc at these electron concentrations. In M2 C the C–C repulsive contribution is sufficiently reduced to allow the hexagonal structure to appear. The opportunity for afurther reduction in this repulsive contribution, together with a change in electrostatic energy, provides a strong tendency for ordering in the C sub lattice of M2 C, leading to high ordering temperatures. MST/3031