群论框架下具有D_(3d)对称性构型的B_2H_6分子的声子间耦合及其杨-泰勒畸变

Studies on the Coupling Among Phonons and the Jahn-Teller Distortion of B_2H_6 Molecules with D_(3d) symmetry Using Group Theory

依据群论与量子理论,利用对称性分析的方法探讨了具有D_(3d)对称性构型的B_2H_6分子的声子间耦合及其杨-泰勒畸变,研究了B_2H_6分子的电子态与声子态的对称性以及其活跃的声子态,导出了B_2H_6分子的e_g声子间耦合的CG系数计算公式,在此基础上进一步计算出了这些CG系数值.接着又分析了B_2H_6分子的杨-泰勒畸变方向及其基态能级的分裂,发现B_2H_6分子的杨-泰勒畸变方向是D_(3d)→C_(2h),畸变导致B_2H_6分子的二重简并的能级发生分裂,因此其能级的简并性因畸变而被完全消除.

Based on group theory and quantum theory, the coupling among phonons and the Jahn- Teller effect of B2H6 molecules with D3d symmetry configuration are studied in this paper, using the methods of symmetry analyses. The symmetry of electronic states and phonon states of B2H6 molecules are studied, it is found that the electronic ground states of B2Ha is Egor E~, the phonon states are a1g, a1v, a2u, e9, eu, and the active phonon state is e9. The CG coefficient formula of eg phonon coupling are derived using projection operators, and these coefficient values are calculated further according to the fornmla obtained. The Jahn-Teller distortion direction and energy level splitting of the system are discussed, it is found that the Jahn-Teller distortion direction of B2H6 molecules should be D3d → C2h, and the original ground energy level of B2H6molecules is split into two energy levels, therefore the electronic degeneracy is completely lifted after the Jahn-Teller distortion.