Ab initio determination of Raman spectra of Mg2SiO4 and Ca2MgSi2O7 showing mixed modes related to LO/TO splitting,Journal of Raman Spectroscopy

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Ab initio determination of Raman spectra of Mg2SiO4 and Ca2MgSi2O7 showing mixed modes related to LO/TO splitting
Journal of Raman Spectroscopy ( IF 2.4 ) Pub Date : 2021-05-04 , DOI: 10.1002/jrs.6129
Krzysztof Parlinski _{1,

2} , Przemysław Piekarz ₁

Affiliation

Density functional theory was used to calculate the nonresonance Raman spectra of forsterite (Mg₂SiO₄) and åkermanite (Ca₂MgSi₂O₇). The Raman tensors are determined from electric polarizibility using finite difference scheme. The Raman reduced spectra (wavenumbers and intensities) are calculated for several typical polarized light scattering geometries for single crystal and polycrystals, demonstrating good agreement with existing published data. In åkermanite, special attention is paid to B₂ and E symmetry phonon modes, which exhibit simultaneous infrared and Raman activities, labeled as mixed representations, and are involved in the longitudinal optic (LO)/transverse optic (TO) splitting. Close to zone-center point, the phonon dispersion curves of mixed modes are analyzed in details, showing for example that mixed modes repulse each other.

中文翻译：

Mg2SiO4 和 Ca2MgSi2O7 的拉曼光谱从头算测定显示与 LO/TO 分裂相关的混合模式

密度泛函理论用于计算镁橄榄石（Mg ₂ SiO ₄）和奥镁石（Ca ₂ MgSi ₂ O ₇）的非共振拉曼光谱。拉曼张量是使用有限差分方案从电极化率确定的。计算了几种典型的单晶和多晶偏振光散射几何结构的拉曼缩减光谱（波数和强度），表明与现有公布的数据非常吻合。在 åkermanite 中，特别注意B ₂和E对称声子模式，同时表现出红外和拉曼活动，标记为混合表示，并参与纵向光学 (LO)/横向光学 (TO) 分裂。靠近区域中心点，详细分析了混合模式的声子色散曲线，例如显示混合模式相互排斥。

更新日期：2021-07-07

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