Relativistic Multireference Perturbation Theory: Complete Active-Space Second-Order Perturbation Theory (CASPT2) With The Four-Component Dirac Hamiltonian
Relativistic Multireference Perturbation Theory: Complete Active-Space Second-Order Perturbation Theory (CASPT2) With The Four-Component Dirac Hamiltonian
复制标题
DOI：
10.1007/978-1-4020-8184-2_6
复制
发表时间：
2008
期刊：
影响因子：
--
通讯作者：
M. Abe;Geetha Gopakmar;T. Nakajima;K. Hirao
中科院分区：
文献类型：
--
作者：
M. Abe;Geetha Gopakmar;T. Nakajima;K. Hirao
本章介绍了四分量相对论哈密顿量的相对论完全活动空间二阶微扰理论(CASPT2)。这种方法可以描述涉及重元素的分子的近简并和解离电子态。该方法适用于既不能用DFT方法也不能用单参考方法描述的系统，也适用于不能用准相对论方法描述的具有重元件的系统。本理论以一种平衡的方式提供了键态或离解态以及基态和激发态的精确描述。本文用Dirac-Coulomb(DC)CASPT2方法计算了6P系列、TlH、Tl2、PbH和Pb2双原子分子的基态和低激发态，给出了它们的光谱常数和势能曲线。将得到的光谱常数与实验结果和前人的理论工作进行了比较。对于所有的分子，DC-CASPT2的光谱常数与实验或以前的理论光谱常数显示出相当好的一致性
The relativistic complete active-space second-order perturbation theory (CASPT2) developed for the four-component relativistic Hamiltonian is introduced in this chapter. This method can describe the near-degenerated and dissociated electronic states of molecules involving heavy elements. This method is applicable for the systems which can be described by neither DFT nor single reference methods, and the system with very heavy-elements which cannot be described by quasi-relativistic approaches. The present theory provides accurate descriptions of bonding or dissociation states and of ground and excited states in a well-balanced way. In this review, for example, the ground and low-lying excited states of diatomic molecules with 6p series, TlH, Tl2, PbH, and Pb2are calculated with the Dirac–Coulomb (DC) CASPT2 method and their spectroscopic constants and potential energy curves are presented. The obtained spectroscopic constants are compared with experimental findings and previous theoretical works. For all the molecules, the spectroscopic constants of DC-CASPT2 show reasonably good agreement with the experimental or previous theoretical spectroscopic constants