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首页> 外文期刊>Geophysical Research Letters >High-temperature dynamics in cristobalite (SiO_2) and carnegieite (NaAlSiO_4): a Raman spectroscopy study
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High-temperature dynamics in cristobalite (SiO_2) and carnegieite (NaAlSiO_4): a Raman spectroscopy study

机译：方石英（SiO_2）和卡耐基石（NaAlSiO_4）的高温动力学：拉曼光谱研究

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摘要

β-cristobalite (SiO_2) and β-carnegieite (NaAlSiO_4) have been investigated by Raman spectroscopy up to their melting points at 1999 and 1799 K, respectively. In both cases, the major spectral changes are observed at the α-β transitions, near 540 and 970 K, especially at low frequencies where the modes, involving mainly intertetrahedral motion, merge to a single, broad envelope. These observations and comparisons made between the Raman spectra of the crystalline and liquid phases are consistent with the rigid-unit model recently proposed for describing the dynamics of SiO_4 and AlO_4 tetrahedra in framework silicates. From a structural standpoint, an important consequence is that the atomic mobility associated with premelting sets in at the low temperatures of these transitions, not in the vicinity of the melting point as for other silicate minerals.
机译：用拉曼光谱法研究了β-方英石（SiO_2）和β-卡耐基石（NaAlSiO_4）的最高熔点分别为1999和1799K。在这两种情况下，在540和970 K附近的α-β跃迁处都观察到了主要的光谱变化，尤其是在低频时，主要涉及四面体运动的模式合并为单个宽包络。晶体和液相的拉曼光谱之间的这些观察和比较与最近提出的用于描述骨架硅酸盐中SiO_4和AlO_4四面体的动力学的刚性单元模型一致。从结构的角度来看，一个重要的结果是与预熔化相关的原子迁移率在这些转变的低温下发生，而不是像其他硅酸盐矿物那样在熔点附近发生。

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