High-pressure IR spectra of lattice modes and OH vibrations in Fe-bearing wadsleyite
High-pressure IR spectra of lattice modes and OH vibrations in Fe-bearing wadsleyite
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含铁瓦兹利石中晶格模式和 OH 振动的高压红外光谱
DOI：
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发表时间：
1994
期刊：
影响因子：
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通讯作者：
A. Hofmeister
中科院分区：
文献类型：
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作者：
H. Cynn;A. Hofmeister
在0 ~ 23 GPa范围内对含铁瓦德利石的大多数晶格模式和含水杂质的高压红外光谱进行了测量。在环境条件下，35个预期红外波段中的29个通过反射和吸收测量的组合显示出来。镁端元在环境条件下的吸收光谱相似。8种氢氧根振动的压力依赖性均为12 GPa。氢键的程度可以从羟基频率的值及其对压力的响应中推断出来：5个低v的羟基具有负的∂v/∂P，因此氢键强度适中，而3个高v的OH基团具有接近零或正值的∂v/∂P，因此氢键强度较弱或没有。利用这些信息，OH波段对Fe/Mg交换的响应，以及X射线数据，将最强的OH波段分配给结构位点O(1)和O(2)。这些羟基振动的分配与以前的理论模型一致。我们对名义无水瓦德斯莱岩中高压OH振动的研究表明，瓦德斯莱岩中的氢杂质在压缩过程中是稳定的。我们的数据与之前观察到的9 GPa左右的微小结构变化是一致的，这可能是由于压缩机制的微小变化。
High-pressure infrared (IR) spectra of most lattice modes and of hydrous impurities of Fe-bearing wadsleyite were measured from O to 23 GPa. At ambient conditions, 29 of the 35 expected IR bands were revealed through a combination of reflection and absorption measurements. Absorption spectra of a magnesium end-member at ambient conditions were similar. The pressure dependence of eight OH vibrations were established to 12 GPa. The degree of hydrogen bonding is inferred from the values of the hydroxyl frequencies and their response to pressure: Five hydroxyls with low v have negative ∂v/∂P and thus moderate to strong hydrogen bonding, whereas three OH groups with high v have near-zero or positive values of ∂v/∂P and thus weak or no hydrogen bonding. This information, the response of the OH bands to Fe/Mg exchange, and X ray data were used to assign the most intense OH bands to the structural sites, O(1) and O(2). These assignments of hydroxyl vibrations are consistent with previous theoretical models. Our study of high-pressure OH vibrations in nominally anhydrous wadsleyite indicates that hydrogen impurities in wadsleyite are stable during compression. Our data are consistent with the previously observed minor structural change at around 9 GPa which is possibly due to a slight change in the compression mechanism.