含旋轨耦合的运动方程耦合簇理论计算闭壳层原子激发能  

Excitation energies of closed-shell atoms based on equation-of-motion coupled-cluster theory with spin-orbit coupling

作　　者：张硕[1] 王治钒 王繁[1] 

机构地区：[1]四川大学原子与分子物理研究所,成都610064

出　　处：《中国科学：化学》2016年第1期80-91,共12页SCIENTIA SINICA Chimica

基　　金：自然科学基金(21273155;21473116)资助

摘　　要：本文采用X2C(exact two-component)哈密顿量,结合我们最近发展的含旋轨耦合的运动方程耦合簇方法,在EOM-CCSD级别上,用接近完备的基函数计算了一系列闭壳层原子体系的最低单重和三重激发能以及激发态的旋轨耦合分裂能.结果显示,对于IIA族原子、IIB族原子、IIIA族阳离子以及稀有气体原子,本文计算得到的激发能与实验值差别通常在0.1 e V以内.对于IB族正离子,由于CCSD方法对其基态存在较大误差,因此激发能被显著高估.对于激发态的旋轨耦合分裂能,前五周期IIA族原子、IIB族原子、IIIA族阳离子计算结果与实验结果吻合非常好,差别通常在1%以内.对于第六周期体系,这个方法得到的激发态旋轨耦合分裂能与实验比有一定误差,这可能是由于求解Hartree-Fock方程时忽略了旋轨耦合所导致.对惰性气体原子,即使是较轻元素,这个方法给出的旋轨耦合分裂能与实验值也有一定差别.In this paper, lowest singlet and triplet excitation energies as well as spin-orbit （SOC） splitting of the triplet states for a series of closed-shell atoms are calculated based on equation-of-motion coupled-cluster theory at the CC singles and doubles level （EOM-CCSD）. The X2C Hamiltonian is employed to account for relativistic effects and a basis set approaching basis sets limit is adopted. According to our results, excitation energies for the IIA, IIB, and rare gas atoms as well as IliA cations are calculated reliably with an error of less than 0.1 eV in most cases. On the other hand, excitation energies are overestimated sizeable for IB cations since CCSD is inadequate in describing the ground state. SOC splitting for triplet states of the first five-row atoms of IIA, liB and IIIA elements is calculated with high accuracy with a deviation of less than 1%. On the other hand, error in SOC splitting for the sixth-row atoms is somewhat larger. This is because SOC is neglected in solving Hartree-Fock equation in the present approach In addition, the calculated SOC splitting for excited states of rare gas atoms does not agree well with experimental values even for light elements.

关 键 词：自旋轨道耦合 X2C哈密顿量 运动方程耦合簇方法 激发能 

分 类 号：O641.1[理学—物理化学]