中文摘要：

在C2v对称性下,采用全活化空间自洽场（CASSCF）和多组态二级微扰理论（CASPT2）方法研究氰基铝（AlCN）及其阴阳离子的基态和低能激发态.在ANO-L基组水平下,计算了AlCN及其阴阳离子低能电子态的几何,组态及其相互作用系数,谐振频率,绝热激发能,垂直激发能和振子强度.在CASSCF/CASPT2理论水平下,计算得到AlCN的11Π电子态的绝热激发能为352.4kJ·mol-1,与实验值344.0kJ·mol-1符合得很好.另外,预测AlCN的跃迁X1Σ＋→21Π发生在673.1kJ·mol-1.激发能和振子强度的计算为研究AlCN的吸收光谱提供理论指导.

英文摘要：

In C2v symmetry,the ground and low-lying excited states of aluminum cyanide （AlCN） and its ions have been studied by using the complete active space self-consistent field （CASSCF） and multicon-figurational second-order perturbation theory （CASPT2） methods. For the low-lying electronic states of AlCN and its ions,the geometries,leading configurations and configuration interaction coefficients,harmonic vibrational frequencies,adiabatic excitation energies,vertical excitation energies and oscillator strengths are calculated with the ANO-L basis sets. At the CASSCF/CASPT2 level,for the 11Π electronic state of AlCN,the adiabatic excitation energy is calculated to be 352.4 kJ·mol-1,which agrees well with the experimental value of 344.0 kJ·mol-1. In addition,the transition X1Σ＋→21Π of AlCN is predicted at 673.1 kJ·mol-1. The calculations of excitation energies and oscillator strengths provide a theoretical guidance to the investigation on absorption spectrum of AlCN.