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本文考查了在某些含稀土ThCr_2Si_2型相中早已观察到的镧系膨胀(相对于镧系收缩而言),并与大多数这种相中所观察到的正常镧系收缩性质进行了比较。很明显镧系膨胀是由于几何因素引起的,即如果一个小的镧系原子代替一个大的镧系原子,只要Si-Si和Si-M(M为非稀土过渡元素)的间距保持不变,则c轴膨胀。形成这些化合物过程中,也发生电子转移。在大多数情况下,电子转移对于镧系膨胀是更重要的。它是镧系膨胀仅发生在RM_2Si_2(M=Cu,Ag)、RCu_2Ge_2和部分RPt_2Si_2系化合物中的原因。
This article examines the lanthanide expansion (relative to lanthanide shrinkage) that has been observed in some rare earth-containing ThCr2Si2-type phases and compares the observed normal lanthanide shrinkage properties in most of these phases. It is clear that the lanthanide expansion is due to the geometric factors that if a small lanthanide atom replaces a large lanthanide atom as long as the spacing between Si-Si and Si-M (M is a non-rare earth transition element) remains constant, C-axis expands. Electron transfer also takes place during the formation of these compounds. In most cases, electron transfer is more important for lanthanide swelling. It is the reason why lanthanide bulking occurs only in RM_2Si_2 (M = Cu, Ag), RCu_2Ge_2 and some RPt_2Si_2 compounds.