GeTe和GeSe 分子在外电场下的特性研究

对Ge原子采用6-311++G^**基函数,Te和Se原子采用SDB-cc-pVTZ基函数,利用密度泛函理论的局域自旋密度近似方法优化得到了GeTe和GeSe分子的稳定构型,并计算了外电场作用下GeTe和GeSe基态分子的平衡核间距、总能量、最高已占据分子轨道能量E_H、最低未占分子轨道能量E_L、能隙、谐振频率和红外谱强度. 在上述计算的基础上利用单激发组态相互作用-局域自旋密度近似方法研究了GeTe和GeSe分子在外电场下的激发特性. 结果表明:随着正向电场强度的增大,分子核间距逐渐增大,分子总能量逐渐降低,谐振频率逐渐减小,红外谱强度则逐渐增大. 在0-2.0569×10¹⁰ V·m^-1的电场范围内,GeTe分子的E_H 均高于GeSe分子的E_H;随着正向电场的增大,GeTe与GeSe的E_H差逐渐变大,GeTe的E_L低于GeSe的E_L,它们的E_L均随正向电场的增大而增大. 无外场时,GeTe分子的能隙比GeSe分子的能隙要小;在外电场反向增大的过程中, GeTe和GeSe的分子能隙始终减小. 外电场的大小和方向对GeTe和GeSe分子的激发能、振子强度及跃迁的波长均有较大影响. 关键词： GeTe GeSe 外电场 激发态

The study of structure characteristics of GeTe and GeSe molecules under the external electric field

Equilibrium structures of the GeTe and GeSe ground state molecules are obtained by employing the local spin density approximation method with 6-311++G^** basis sets for Ge and SDB-cc-pVTZ for Te and Se. Also obtained are the equilibrium geometry, the highest occupied molecular orbital(HOMO) energy level, the lowest unoccupied molecular orbital(LUMO)energy level, the energy gap, the harmonic frequency and the infrared intensity of GeTe and GeSe ground state molecules under different electric fields. On the basis of the above calculation, the excited states of GeTe and GeSe molecules under different electric fields are also investigated by using the single-excitation configuration interaction-local spin density approximation method. The results show that the equilibrium internuclear distance and the intensity of infrared are found to increase, but the total energy and harmonic frequency are proved to decrease with the increase of positive direction electric field. The HOMO energy E_H of GeTe molecule is higher than that of GeSe molecule under electric fields ranging from 0 to 2.0569×10¹⁰ V ·m^-1. For GeTe and GeSe molecules, their difference in E_H gradually increases with the increase of positive direction electric field. The LUMO energy E_L of GeTe molecule is lower than that of GeSe molecule, and their LUMO energies are found to increase with the increase of positive direction electric field. The energy gap of GeTe is low than that of GeSe, and their energy gaps always decrease with the increase the negative direction electric field. The magnitude and the direction of the external electric field have important effects on excitation energy, oscillator strength and wavelength.