Local relaxation around Fe3+ in fluorides:: Influence on electronic properties
Local relaxation around Fe3+ in fluorides:: Influence on electronic properties
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DOI：
10.1103/physrevb.61.6525
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发表时间：
2000-03-01
影响因子：
3.7
通讯作者：
Moreno, M
中科院分区：
文献类型：
--
作者：
Aramburu, JA;Paredes, JI;Moreno, M
通过密度泛函（DF）计算，探讨了不同氟化物晶格中Fe3+杂质周围的局部弛豫。为了同样的目的，我们还利用自一致电荷扩展Huckel方法和多重散射X α方法研究了各向同性超细常数A(s)对金属-配体距离R的依赖关系。在所有情况下，发现A(s)与R(-n)sn(s)成正比，介于6和7.5之间。根据这一结果，CsCdF3:Fe3+和KMgF3:Fe3+的平衡距离δ R-e仅等于两个系统的电子-核双共振（ENDOR）数据的2.3 pm左右。这个图必须与对应于完美主晶格的δ R-0 = 23 pm的值进行比较，它与由总能量计算得出的R-e值是相容的。虽然δ R-e = 2.3 pm远小于相同晶格中Mn2+对应的δ R-e = 7+/-1 pm，但这两种杂质的w（A(1g)）频率是一致的。从目前的结果来看，静水压力降至0.05 pm引起的R-e变化可以通过ENDOR测量的a (s)变化来检测。此外，还指出，从簇上的DF计算可以得到绝缘体中过渡金属杂质的实际杂质配体距离的良好信息。最后，10Dq值及其R依赖性与反键e(g)*能级的小3d-2s(F)杂化密切相关，这也决定了A(s)。
The local relaxation around Fe3+ impurities in different fluoride lattices has been explored by means of density-functional (DF) calculations on clusters including up to third neighbors of Fe3+. For the same purpose the dependence of the isotropic superhyperfine constant, A(s), on the metal-ligand distance, R, has been studied for clusters of different size using the self-consistent charge extended Huckel and multiple-scattering X alpha methods as well. In all cases A(s) is found to be proportional to R(-n)sn(s) lying between 6 and 7.5. Using this result the difference, Delta R-e, between the equilibrium distance for CsCdF3:Fe3+ and KMgF3:Fe3+ would be equal only to about 2.3 pm from the electron-nuclear double resonance (ENDOR) data reported for both systems. This figure, which has to be compared with the value Delta R-0 = 23 pm corresponding to the perfect host lattice, is compatible with the R-e values derived from total-energy calculations. Although the value Delta R-e = 2.3 pm is much smaller than Delta R-e = 7+/-1 pm corresponding to Mn2+ in the same lattices, it is shown to be consistent with the w(A(1g)) frequency for both kind of impurities. From the present results R-e changes caused by a hydrostatic pressure down to 0.05 pm can be detected through A(s) variations measured by ENDOR. Moreover it is pointed out that good information about the actual impurity-ligand distance for transition-metal impurities in insulators can be obtained from DF calculations on clusters. Finally, the 10Dq value and its R dependence are shown to be strongly related to the small 3d-2s(F) hybridization in the antibonding e(g)* level which also determines A(s).