TEMPERATURE-DEPENDENCE OF TRANSVERSE AND LONGITUDINAL OPTIC MODES IN ALPHA-PHASES AND BETA-PHASES OF QUARTZ
TEMPERATURE-DEPENDENCE OF TRANSVERSE AND LONGITUDINAL OPTIC MODES IN ALPHA-PHASES AND BETA-PHASES OF QUARTZ
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DOI：
10.1103/physrevb.11.3944
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发表时间：
1975-01-01
影响因子：
3.7
通讯作者：
PIRIOU, B
中科院分区：
文献类型：
--
作者：
GERVAIS, F;PIRIOU, B
本文报道了石英在α和β相的红外反射率光谱（a2 -和e型振动模式）的温度依赖性，重点研究了α→β相变的附近。根据介电函数的因式分解形式，用四参数色散模型拟合了光谱，该模型允许确定TO和LO频率和阻尼的温度依赖性。2个a2模和3个E模（本文研究的6个E模中）在β相中被禁止，并且在相变接近时临界地失去极性特征。在温度c= 846 K附近，α相中一些模态的频率发生了临界软化或硬化。与热晶格膨胀的比较表明，这种临界行为可以从纯体积效应的角度来理解。在α相中，模式衰减在跃迁附近发散，而在300-700 K范围内和β相中，声子寿命受到非谐波三声子耦合的限制。
The temperature dependence of the infrared reflectivity spectra (A 2− and E-type vibrational modes) of quartz is reported in the α and β phases with emphasis on the vicinity of the α→ β phase transition. Spectra have been fitted with a four-parameter dispersion model based on the factorized form of the dielectric function that allows the temperature dependence of the TO and LO frequencies and damping to be determined. Two A 2 and three E modes (among the six E modes studied here) are forbidden in the β phase, and they critically lose their polar character at the approach of the phase transition. The frequencies of a number of modes critically soften or harden in the α phase, in the vicinity of T c= 846 K. A comparison with thermal lattice expansion indicates that this critical behavior might be understood in term of pure volume effect. In the α phase, mode dampings diverge in the vicinity of the transition whereas in the range 300-700 K and in the β phase, phonon lifetimes appear limited by anharmonic three-phonon coupling.