Structural and electronic relationships between the lanthanide and actinide elements
Structural and electronic relationships between the lanthanide and actinide elements
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镧系元素和锕系元素之间的结构和电子关系
DOI：
10.1023/a:1012667128586
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发表时间：
2000
影响因子：
--
通讯作者：
B. Johansson
中科院分区：
文献类型：
--
作者：
B. Johansson
指出了4f和5f过渡金属固态性质的异同。较重的 5f 元素表现出与早期 4f 过渡金属直接对应的特性，表明这些金属的 5f 电子具有局域行为。另一方面，Pu 金属的体积比其邻近的较重元素 Am 低 30%，这一事实表明该元素的 5f 电子特性相对于较重的锕系元素存在巨大差异。 Pu 和 Am 之间的这种行为变化可以被视为 5f 壳层内的莫特转变，作为原子序数 Z 的函数。在莫特转变的金属 5f 侧（即早期锕系元素），这些元素显示出最不寻常的晶体结构，共同特征是它们的低对称性。在压缩下的铈金属中发现了镧系元素的类似行为，其中轻锕系元素的典型结构已通过实验观察到。锕系元素的广义相图显示出包含与 Ce 金属的单独相图相当的特征。镧系元素和较重锕系元素的晶体结构行为由金属态下 5d（或 6d）电子的数量决定，因为对于这些元素，f 电子是局域且非键合的。对于早期的锕系金属电子结构计算（其中 5f 轨道被视为价带的一部分）很好地解释了观察到的基态晶体结构。扭曲结构可以理解为远离对称 bcc 结构的 Peierls 扭曲，源自占据相对较窄 5f 态的强键合 5f 电子。高压是证明镧系元素和锕系元素之间相互关系的极其有用的实验工具。
The similarity and difference between the solid state properties of the 4f and 5f transition metals are pointed out. The heavier 5f elements show properties which have direct correspondence to the early 4f transition metals, suggesting a localized behaviour of the 5f electrons for those metals. On the other hand, the fact that Pu metal has a 30% lower volume than its neighbour heavier element, Am, suggests a tremendous difference in the properties of the 5f electrons for this element relative to the heavier actinides. This change in behaviour between Pu and Am can be viewed as a Mott transition within the 5f shell as a function of the atomic number Z. On the metallic 5f side of the Mott transition (i.e., early actinides), the elements show most unusual crystal structures, the common feature being their low symmetry. An analogous behaviour for the lanthanides is found in cerium metal under compression, where structures typical for the light actinides have been observed experimentally. A generalized phase diagram for the actinides is shown to contain features comparable to the individual phase diagram of Ce metal. The crystal structure behaviour of the lanthanides and heavier actinides is determined by the number of 5d (or 6d) electrons in the metallic state, since for these elements the f electrons are localized and nonbonding. For the earlier actinide metals electronic structure calculations - where the 5f orbitals are treated as part of the valence bands - account very well for the observed ground state crystal structures. The distorted structures can be understood as Peierls distortions away from the symmetric bcc structure and originate from strongly bonding 5f electrons occupying relatively narrow 5f states. High pressure is an extremely useful experimental tool to demonstrate the interrelationship between the lanthanides and the actinides.