若干双原子及三原子分子的势能函数与光谱性质的研究

In the present work, high level ab initio calculations are carried out for some diatomics and triatomic molecules. In order to obtain accurate potential energy curves (PECs), various corrections (core-valence correlation, relativistic corrections, basis set truncation, adiabatic approximation, spin-orbit coupling, etc.) are included. Based on the study of the applicability of the potential energy function (PEF) models, the test adopted the curve piecewise fitting method to build up a new PEF form. Then the PECs including the corrections are fitted to correcting PEFs. Using these present PEFs, the spectroscopic and vibrational manifold calculations, such as the spectroscopic parameters, the vibrational levels, the classical turning points, the inertial rotation and the centrifugal distortion constants, are investiged. The lack of spectroscopic and molecular constants hinder the applications the application in various fields of some molecules. For these molecules, the present results should be good references for future laboratory research.

本项目利用从头计算研究若干双原子分子及三原子分子的势能曲线，并在确定的理论水平下修正各种因素（核价相关、相对论、基组截断、绝热近似、旋轨耦合等）对势能曲线的影响，以期获得精确的势能曲线.其中通过能量外推的方法修正基组截断对势能曲线的影响.根据对目前势能函数解析模型实用性的研究，对势能曲线进行分段拟合，建立一个新的势能函数形式. 根据新的势能函数形式对考虑各种修正后的势能曲线进行拟合，得到这些分子的势能函数,该势能函数能更精确地反映了分子的性质.根据得到的势能函数，进一步研究分子的光谱性质(光谱常数、分子常数、振转跃迁等). 本项目对那些缺乏实验数据的分子，可以预测其势能函数及光谱性质，对其在各领域的应用具用重要的指导意义.

本项目的研究工作按照原定计划执行，取得一系列预期成果。我们对多个小分子体系（SiN、SO、P2+、AsP和As2）进行了研究，采用多种理论方法（MRCI、MR-ACPF、UCCSD（T））结合相关一致基对这些分子进行了相对论、核价相关、Davidson以及基组截断误差的修正，并进一步确定这些修正对体系能量及光谱性质的影响。进一步研究证明这些修正改善了分子的光谱常数和分子常数。