The effect of redox state on the local structural environment of iron in silicate glasses:: a molecular dynamics, combined XAFS spectroscopy, and bond valence study
The effect of redox state on the local structural environment of iron in silicate glasses:: a molecular dynamics, combined XAFS spectroscopy, and bond valence study
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DOI：
10.1016/j.jnoncrysol.2004.07.050
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发表时间：
2004-10-01
影响因子：
3.5
通讯作者：
Brown, GE
中科院分区：
文献类型：
--
作者：
Farges, F;Lefrère, Y;Brown, GE
一系列27种不同组成的硅酸盐玻璃，其含有0.2-2原子%在各种氧逸度值下合成铁。使用X射线吸收精细结构（XANES）光谱法在Fe K-边检查玻璃，以确定铁的氧化态和第一近邻配位数。光谱信息提取的前边缘区域和主成分分析（PCA）的XANES区域，连同光谱反演，被用来获得的端员光谱成分为Fe（II）和Fe（III）。在边缘前的功能的线性趋势，观察到作为Fe（II）/Fe（III）含量的函数检查的玻璃的大多数组成系列。这些线性趋势被认为是由于在每个系列中Fe（II）和Fe（III）端元的平均配位数的相似性。这一结果是一致的模型模拟的XANES区域和分子动力学（MD）模拟的两个端员组成，这也表明，Fe（II）和Fe（III）具有相似的平均配位数。这些模拟还表明存在五配位的Fe（III）在熔体相中。基于这些分子动力学模拟的键价分析，提出了一个简单的模型，以帮助预测氧化物和硅酸盐玻璃和熔体中的铁的形态。(C)2004 Elsevier B. V.保留所有权利。
A series of 27 silicate glasses of various compositions containing 0.2-2 at.% iron were synthesized at various oxygen fugacity values. The glasses were examined using X-ray absorption fine structure (XANES) spectroscopy at the Fe K-edge in order to determine iron oxidation state and first-neighbor coordination number. Spectral information extracted from the pre-edge region and principal component analysis (PCA) of the XANES region, together with a spectral inversion, were used to derive the end-member spectral components for Fe(II) and Fe(III). Linear trends in the pre-edge features were observed for most compositional series of the glasses examined as a function of Fe(II)/Fe(III) content. These linear trends are believed to be due to the similarity of average coordination numbers for both Fe(II) and Fe(III) end-members in each series. This result is consistent with model simulations of the XANES region and molecular dynamics (MD) simulations for the two end-member compositions which also show that Fe(II) and Fe(III) have similar average coordination numbers. These simulations also suggest the presence of five-coordinated Fe(III) in the melt phase. Based on a bond valence analysis of these MD simulations, a simple model is proposed to help predict the speciation of iron in oxide and silicate glasses and melts. (C) 2004 Elsevier B.V. All rights reserved.