Ti K-edge XANES studies of Ti coordination and disorder in oxide compounds: Comparison between theory and experiment
Ti K-edge XANES studies of Ti coordination and disorder in oxide compounds: Comparison between theory and experiment
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DOI：
10.1103/physrevb.56.1809
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发表时间：
1997-07-15
影响因子：
3.7
通讯作者：
Rehr, JJ
中科院分区：
文献类型：
--
作者：
Farges, F;Brown, GE;Rehr, JJ
将各种含 Ti(IV) 晶体氧化物模型化合物的实验 Ti K 边 X 射线吸收近边结构 (XANES) 光谱与使用从头算多次散射代码 FEFF7 计算的光谱进行了比较。对实验光谱中各种特征（包括前边缘和主边缘峰值）的散射理论解释以及对无序效应的解释一起提出。发现观察到的边缘前特征在位置（大约 2 +/- 0.1 eV）和归一化高度（从大约 0.04 到 1.0 +/- 0.05）作为 Ti 配位（4、5 或 6 个氧最近邻）的函数而变化，与计算一致。在 Ti 配位未知的非周期性氧化物化合物（例如钛硅酸盐玻璃和熔体）中，预边缘位置和高度可用于获得有关 Ti 配位化学的可靠信息。例如，人们可以区分五重配位 Ti（即 TiO5）和四重和六重配位 Ti 的 50:50 混合物（即 TiO4 与 TiO6）。最后，提出主边缘特征的强度可以作为Ti中短程环境无序度的探针。 Ti XANES 研究辐射损伤对 CaTiSiO5 的影响以及 K2TiSi2O7 玻璃在高温下的熔化就证明了这一点。
Experimental Ti K-edge x-ray-absorption near-edge structure (XANES) spectra for a variety of Ti(IV)bearing crystalline oxide model compounds are compared with those calculated using the ab initio multiple-scattering code FEFF7. A scattering-theoretic interpretation of various features in the experimental spectra, including pre-edge and main-edge peaks, is presented together with an interpretation of the effects of disorder. The observed pre-edge features are found to vary in both position (by approximate to 2 +/- 0.1 eV) and normalized height (from approximate to 0.04 to 1.0 +/- 0.05) as a function of Ti coordination (4, 5, or 6 oxygen nearest neighbors), in agreement with calculations. In aperiodic oxide compounds where the Ti coordination is unknown (e.g., titanosilicate glasses and melts), pre-edge position and height can be used to derive reliable information on Ti coordination chemistry. For example, one can distinguish between fivefold coordinated Ti (i.e., TiO5) and a 50:50 mixture of fourfold-and sixfold-coordinated Ti (i.e., TiO4 vs TiO6). Finally, it is proposed that the intensity of the main-edge features can be used as a probe of disorder in the short-and medium-range environment of Ti. This is exemplified by Ti XANES studies of the effect of radiation damage on CaTiSiO5 and the melting of K2TiSi2O7 glass at high temperature.