采用密度泛函理论的B3LYP方法, 在6-311G++(d,p)基组水平上优化了不同外电场(0～0.025 a.u.)下氮化镓分子的基态稳定构型, 在此基础上利用同样的方法计算了氮化镓分子的分子结构、 偶极矩、 总能量、 能隙以及红外光谱, 拉曼光谱, 紫外-可见吸收光谱强度。 结果表明, 分子的结构的变化与电场大小呈现强烈的依赖关系。 随着正向外加电场的增加, GaN分子键长不断减小, 电偶极距不断减小, 分子总能量不断增大, 分子能隙不断减小, 红外光谱吸收峰出现蓝移现象, 拉曼光谱出现蓝移现象。 随着外电场的加强, 分子紫外-可见吸收光谱振子强度出现先减小后增大再减小的反复变化, 其波峰则出现红移现象。

Based on the density functional theory DFT/B3LYP at 6-311++g(d, p) level, the ground states of GaN molecule under different external electric fields were optimized. The influence of external electric field ranging from 0 to 0.025 a.u. on the geometrical parameters, dipole moment, total energy, energy gap, Infrared spectrum, Raman spectrum and UV-VIS absorption spectrum intensity were studied. The results showed that the changes of molecular structure were strongly dependent on the applied electric field. As the electric field changed from 0 to 0.025 a.u., the bond length of GaN molecular decreased, while the electric dipole moment was proved to be decreasing and the total molecular energy increased all the time. The energy gap of Eg was found to decrease with the increasing external field. The IR vibration spectrum of GaN molecule showed an observable blue shift and the Raman vibration spectrum appears blue shift phenomenon too. The oscillator strength of UV-VIS absorption spectrum was proved to be repeating the changes of the first decreasing and then increased. The ultraviolet absorption peak was red-shifted with the increase of the field intensity.