中文摘要：

以6-311＋＋G（d,p）为基组,采用密度泛函的B3LYP方法优化得到不同外电场（-0·03—0·045a.u.）下CaS分子的基态结构参数、电偶极矩μ、电荷分布、HOMO能级、LUMO能级、能隙、红外光谱和谐振频率等.结果表明,随着正向电场的增加,分子结构与外电场有着强烈的依赖关系,且对电场方向的依赖呈现出不对称性,基态键长和分子偶极矩μ先减小后增大,在F=0·02a.u.时,键长Re取最小值0·2289nm,电偶极矩取最小值1·5969D,HOMO能级和LUMO能级处于先增大后减小,能隙始终是减小的,占据轨道的电子容易激发到空轨道.外电场对CaS分子的激发能和振子强度有较大的影响,这为进一步研究它的电致发光机理提供了一定的理论基础.

英文摘要：

The method B3LYP of the density functional theory （DFT） at 6-311＋＋G（d, p） level has been used to obtain equilibrium structure of the ground state of CaS molecule, optimized parameters, dipole moment, charge distribution, HOMO energy level, LUMO energy level, energy gaps, infrared spectrum and harmonic frequency under different external electric fields rang ing from -0.03 a.u. to 0.045 a.u. The results shows that with increasing the external electric field, the molecular geometry becomes strongly dependent on the field strength and behaves asymmetrically to the direction of the applied electric field. At the same time, the bond length and dipole moment μ of the ground state are changed from decreasin g to increasing. At F=0.02 a.u., the minimum of bond length and dipole moment are 0.2289 nm and 1.5969 D. HOMO energy level and LUMO energy level are changed from increasing to decreasing. A decrease of the total energy gaps are found in the process of increasing the external electric field, which tells that the molecule is excited easily under a specific electric field. Excitation energies and oscillator strengths are affected by the external electric field. These results are useful for the study on the electroluminescence of CaS molecule.