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应用计及五阶近邻的力常数模型,研究了单轴应力下的石墨烯和芳香烃分子三明治型贴层的石墨烯中拉曼谱的G峰劈裂.计算结果表明对称性的降低解除了G峰对应的在Γ点的面内的纵波光学模声子和横波光学模声子能量简并,从而G峰劈裂为G+和G-两个峰.在单轴应力作用下,C—C键的伸长致使力常数减小,软化了面内的光学模声子,导致两个G峰都红移;芳香烃分子对石墨烯产生的沿分子长短边方向不同的应力作用,使得G峰对应的两支光学模声子的频率一支发生蓝移,而另一支发生红移.这解释了两种应力情况下石墨烯的拉曼谱实验中G峰不同的劈裂现象.
The G-mode splitting of graphene in graphene with graphene and aromatic molecular sandwich with uniaxial stress is studied by using the force constant model with fifth-order nearest neighbor. The calculation results show that the symmetry is reduced The G-peak splits into G + and G- peaks due to the degeneracy of the longitudinal mode optical mode phonons and transverse mode optical phonons at the Γ point, and the C-C Elongation of the bond results in a decrease of the force constant and softens the in-plane optical mode phonons, resulting in red shifts of both G peaks. The aromatic molecules exert different stresses on the graphene along the length and width of the molecule, The corresponding two modes of optical phonons are blue-shifted in frequency and red-shifted in the other, which explains the different cleavage of G-peak in graphene Raman spectra under two stress conditions.