High-temperature Raman spectra of natural sillimanite, andalusite and kyanite were measured in the temperature range of 296–1273 K at ambient pressure. No phase transition was observed over the temperature range in this study. Raman modes for the three samples vary with temperature linearly. The temperature and pressure dependence of the force constants for Si–O stretching vibrations in Al 2 SiO 5 polymorphs were determined. The isobaric mode Grüneisen parameters of sillimanite, andalusite, and kyanite were determined from the temperature dependent of present high-temperature Raman spectra and previous results of thermal expansion coefficients. The intrinsic anharmonic mode parameters were estimated and nonzero, indicating the existence of intrinsic anharmonicity for sillimanite, andalusite and kyanite. Based on Kieffer model, the thermodynamic parameters, including isochoric heat capacity and entropy, were calculated.

中文翻译：

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不同温度下硅线石、红柱石和蓝晶石的拉曼光谱

天然硅线石、红柱石和蓝晶石的高温拉曼光谱在 296-1273 K 的温度范围内在环境压力下测量。在本研究中，在整个温度范围内未观察到相变。三个样品的拉曼模式随温度线性变化。确定了 Al 2 SiO 5 多晶型物中 Si-O 伸缩振动的力常数的温度和压力依赖性。硅线石、红柱石和蓝晶石的等压模式 Grüneisen 参数是根据当前高温拉曼光谱的温度相关性和热膨胀系数的先前结果确定的。固有非谐模参数经估计且非零，表明硅线石、红柱石和蓝晶石存在固有非谐性。基于基弗模型，