Residual-density mapping and site-selective determination of anomalous scattering factors to examine the origin of Fe K pre-edge peak of magnetite
Residual-density mapping and site-selective determination of anomalous scattering factors to examine the origin of Fe K pre-edge peak of magnetite
复制标题
剩余密度测绘和异常散射因子的位点选择性测定，以检查磁铁矿 Fe K 前边缘峰的起源
DOI：
10.1107/s0909049512031147
复制
发表时间：
2012
影响因子：
2.5
通讯作者：
T. Yasue and S. Sasaki
中科院分区：
文献类型：
--
作者：
M. Okube;T. Yasue and S. Sasaki
用x射线共振散射法分析了磁铁矿中铁离子的电子密度分布及其对异常散射因子的贡献。利用传统的四圆衍射仪在右手圆偏振下进行了同步加速器x射线实验。差分-傅立叶合成应用于在预边缘上和边缘外测量的结构因子的差异（Eon = 7.1082 keV, Eoff = 7.1051 keV）。由于x射线共振散射导致的电子密度峰在A点和B点都被清楚地观察到。反常散射因子f '的实数部分已经根据晶体结构的改进而独立于位置确定，以最小化Fe - K前边缘的平方残差。在Eon和Eoff得到的A位点f′值分别为- 7.063和- 6.682，B位点f′值分别为- 6.971和- 6.709，明显小于Kramers-Kronig变换估计的- 6.206和- 5.844。在Eon处的f ‘值比在Eoff处的f ’值小得多。我们使用基于对称性的考虑结果表明，边缘前峰的起源是同时占据a和B位的铁离子，其中需要p-d混合，两个位置上的铁杂化电子与邻近的O原子重叠。
The electron-density distribution and the contribution to anomalous scattering factors for Fe ions in magnetite have been analyzed by X-ray resonant scattering at the pre-edge of Fe K absorption. Synchrotron X-ray experiments were carried out using a conventional four-circle diffractometer in the right-handed circular polarization. Difference-Fourier synthesis was applied with a difference in structure factors measured on and off the pre-edge (Eon = 7.1082 keV, Eoff = 7.1051 keV). Electron-density peaks due to X-ray resonant scattering were clearly observed for both A and B sites. The real part of the anomalous scattering factor f′ has been determined site-independently, based on the crystal-structure refinements, to minimize the squared residuals at the Fe K pre-edge. The f′ values obtained at Eon and Eoff are −7.063 and −6.682 for the A site and −6.971 and −6.709 for the B site, which are significantly smaller than the values of −6.206 and −5.844, respectively, estimated from the Kramers–Kronig transform. The f′ values at Eon are reasonably smaller than those at Eoff. Our results using a symmetry-based consideration suggest that the origin of the pre-edge peak is Fe ions occupying both A and B sites, where p–d mixing is needed with hybridized electrons of Fe in both sites overlapping the neighbouring O atoms.