利用复杂晶体化学键的平均能带模型研究了LaMAl11O19(M＝Mg,Fe)晶体的化学键性质。结果表明，La-O键只有3%的共价性，4f1格位却具有很强的共价特征。晶体中各格位共价次序为：La-O＜Al(5)-O＜Al(1)-O＜Al(4)-O＜Al(2)-O＜Al(3)-O＜M-O。其中2d格位和4e格位具有强的各向异性特征。利用由共价性和极化率定义的化学环境因子h计算了LaFeAl11O19中57Fe的穆斯堡尔同质异能位移和LaMgAl11O19∶Eu中151Eu的同质异能位移，所得结果与实验值一致。
The chemical bond properties of the magnetoplumbite type compound LaMAl11O19(M＝Mg,Fe) have been studied by using the average band-gap model of the complex crystal chemical bond.The results show that covalency of La-O bond is only 3%,but 4f1 site has very high covalent character in each bond.The covalency for each bond obeys the following order:La-O＜Al(5)-O＜Al(1)-O＜Al(4)-O＜Al(2)-O＜Al(3)-O＜M-O.The anisotropy character in 2d site and 4e site of the crystals is revealed by calculating the chemical bond parameters.Mossbauer isomer shifts of Fe2+ ion in LaFeAl11O19 and Eu3+ ion in LaMgAl11O19 are calculated by using the chemical surrounding facter,h,definited by covalency and electronic polarizability,and the results are in agreement with the experimental values.
参考文献
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