SnSe分子外场下的基态性质和激发态性质

对Sn原子使用SDB-cc-pVTZ基组, Se原子采用6-311++G^**基组, 利用密度泛函中的B3LYP方法研究了电场强度为-0.04–0.04 a.u.的外电场对SnSe基态分子的几何结构、 电荷布居分布、 HOMO能级、 LUMO能级、 能隙、 费米能级、 谐振频率和红外光谱强度的影响. 继而使用含时密度泛函(TD-B3LYP) 方法研究了SnSe分子在外场下的激发特性. 结果表明, 外电场的大小和方向对SnSe分子基态的这些性质有明显影响. 在所加的电场范围内(-0.04 a.u.–0.04 a.u.), 随着正向电场的增大, 核间距先减小后增大, 在F=0.03 a .u.时取得最小值0.2317 nm; 分子电偶极矩μ近似线性地增大; E_L, E_H、 费米能级E_F和能隙E_g均减小. 随着正向电场逐渐增大, 分子总能量和谐振频率均先增大后减小; 红外谱强度则先减小后增大, 在F=0.03 a.u.时, 取得最小值 0.1138 km·mol^-1. 由基态到第1–10个单重激发态的波长均随着正向电场的增大而增大. 激发能均随着正向电场的增大而减小. 电场的引入可改变SnSe分子激发态出现的顺序并使得一些禁止的跃迁变得可能.关键词：SnSe外电场能隙激发特性

The ground state properties and excitation properties for the SnSe molecule under different external electric fields

Effects of electric field ranging from -0.04 to 0.04 a.u., on the equilibrium structure, mulliken atomic charges, the highest occupied molecular orbital(HOMO) energy level, the lowest unoccupied molecular orbital(LUMO) energy level, energy gap, fermi energy, harmonic frequency and infrared intensities of SnSe ground state molecule are investigated by employing density functional (B3LYP) method with SDB-cc-pVTZ for Sn atom and 6-311++G** basis sets for Se atom. The magnitude and direction of the external electric field have significant effects on these characteristics of SnSe molecule. The results show that the bond length is proved to be first decreasing, and then increasing with the increase of the external field, and the minimum value is 0.2317 nm when the field strength is equal to 0.03 a.u.; electric dipole moment is found to increase linearly with the increase of external field, but the HOMO energy E_H, LUMO energy E_L, energy gap E_g and fermi energy E_F are proved to decrease with the increase of external field. The total energy and harmonic frequency are found to first increase, and then decrease, but the infrared intensities are proved to first decrease, and then increase. The wavelengths from ground state to the first ten excited states are found to increase, but the excited energies are decreasing with the increase of the external field. Meanwhile, the sequence of excited states for SnSe molecule can be changed, and some prohibited transition can be allowed under an external field.