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首页> 外文期刊>Acta Crystallographica, Section B. Structural Science >A bond-valence investigation of two series of isostructural lanthanide compounds
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A bond-valence investigation of two series of isostructural lanthanide compounds

机译：两个系列同构镧系元素化合物的键价研究

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Since the days of Pauling it has been tacitly assumed that the valence, which is distributed between the bonds to neighbouring atoms, is the stoichiometric valence, V-stoich, which has integer values. It is shown here that this is not true. Instead, bond-valence sums (BVS) calculated for lanthanide (Ln) atoms of a series of garnet-type compounds Ln(3)(III)Te(2)(VI)Li(3)(I)O(12) deviate significantly from V-stoich. Values of ( BVS) Ln of this series, plotted versus the element number Z(Ln), show the same irregular sequence as: (i) the third ionization potentials of Ln atoms, (ii) the valence values previously calculated with quantum-chemical methods for lanthanide metals and sulfides, and (iii) the experimental efficiencies of the reactions between Ln I and SF6 in the gas phase. This indicates that in the Ln(3)Te(2)Li(3)O(12) series the BVS values of the Ln atoms, which are 'rattling' in rather large and rigid voids of the structure, reflect the electronic structure of Ln. It is, therefore, concluded that BVS represent a non-integer valence, which is based on the electronic structure of bonded atoms, rather than stoich V. For this non-integer valence the term 'structural valence' and the symbol V-struct have been proposed. In another series of lanthanide chelates the ( BVS) Ln values deviate even more from V-stoich(Ln) = 3 v.u. than in the garnet-type series. In the chelates the Ln atoms are 'squeezed' in rather small voids so that the electronic effects of Ln acting on ( BVS) Ln are overridden by stronger steric effects exerted by the organic ligands.
机译：自鲍林时代以来，就一直默认地认为，分布在与相邻原子的键之间的化合价是化学计量化合价V-stoich，它具有整数值。这里表明这是不正确的。取而代之的是，为一系列石榴石型化合物Ln（3）（III）Te（2）（VI）Li（3）（I）O（12）的镧系元素（Ln）原子计算的键合价和（BVS）偏离明显来自V-stoich。相对于元素编号Z（Ln）绘制的该系列（BVS）Ln的值显示出与以下相同的不规则序列：（i）Ln原子的第三电离势，（ii）先前用量子化学方法计算的化合价镧金属和硫化物的方法，以及（iii）Ln I和SF6在气相中反应的实验效率。这表明在Ln（3）Te（2）Li（3）O（12）系列中，Ln原子的BVS值“嘎嘎”在结构的相当大的刚性空隙中，反映了Ln（3）的电子结构。 Ln。因此，可以得出结论，BVS表示非整数化合价，该价是基于键合原子的电子结构而不是stoichV。对于这种非整数化合价，术语“结构化合价”和符号V-struct具有被提出。在另一系列的镧系元素螯合物中，（BVS）Ln值甚至偏离V-stoich（Ln）= 3v.u。比石榴石类型的系列要多。在螯合物中，Ln原子被“压缩”在很小的空隙中，因此，Ln作用于（BVS）Ln的电子效应被有机配体所产生的更强的空间效应所覆盖。

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