外电场下CdSe的基态性质和光谱特性研究∗

摘要

Density functional theoretical (B3PW91) method with LANL2 DZ basis sets has been used to study the equilibrium structure, total energy, the highest occupied molecular orbital (HOMO) energy level, the lowest unoccupied molecular orbital(LUMO) energy level, energy gap, dipole moment, atomic charge distribution, infrared intensities of CdSe ground state molecule etc. in different intense electric fields. The excitation energy, wavelengths and oscillator strengths in ground state and the first nine different excited states are investigated by the time-dependent density functional (B3PW91) method in external electric fields. Results show that the excitation wavelength is in agreement with the experimental result and the excitation energy is close to the experimental data. With the increase of the external field, the bond length, electric dipole moment, infrared intensities are observed to decrease first, and increase afterwards. But the HOMO energy, LUMO energy, energy gap are seen to decrease. And the total energy and harmonic frequency are found to increase first, and then decrease. In addition, the external electric fields have significant effects on the excitation energy, wavelength and oscillator strengths of CdSe molecule.%采用密度泛函(DFT)B3PW91方法在Lanl2dz基组下优化得到CdSe分子的基态稳定构型，并研究了外电场对CdSe基态分子的总能量、HOMO能级、LUMO能级、能隙、电偶极矩µ、电荷布居、红外光谱的影响。在相同的基组下用TD-DFT 方法计算了外电场下CdSe分子的前9个激发态的激发能、激发波长和振子强度。结果表明：无电场时CdSe分子的激发波长与实验结果符合较好，相应的激发能也很接近。随着电场增加， CdSe基态分子键长、偶极矩、红外谱强度先减小后增大； HOMO能级、LUMO能级、能隙随电场增加而减小；总能量、谐振频率则是先增大后减小。此外，外电场对CdSe分子的激发能，激发波长和振子强度均有较大影响。