Hršak Dalibor, Olsen Jógvan Magnus Haugaard, Kongsted Jacob
Department of Physics, Chemistry and Pharmacy , University of Southern Denmark , Campusvej 55 , 5230 Odense M , Denmark.
J Chem Theory Comput. 2018 Mar 13;14(3):1351-1360. doi: 10.1021/acs.jctc.7b01153. Epub 2018 Feb 23.
We present the theory and implementation of the polarizable density embedding (PDE) model in combination with coupled cluster (CC) theory (PDE-CC). This model has been implemented in the Dalton quantum chemistry program by adapting the CC code to the polarizable embedding library ( PElib). In the PDE-CC method, the smaller, but chemically important core region is described with a high-level CC method. The environment surrounding the core region can be separated into two levels of description: an inner and an outer region. The effect of the inner region on the core region is described by an embedding potential consisting of a set of fragment densities obtained from calculations on isolated fragments with a quantum-chemistry method such as Hartree-Fock (HF) or Kohn-Sham density functional theory (KS-DFT) and dressed with a set of atom-centered anisotropic dipole-dipole polarizabilities. The outer region consists of distributed atom-centered multipoles and polarizabilities, i.e., in the same way as in the polarizable embedding (PE) model. The PDE-CC method contains embedding potential operators that account for the electrostatic and polarization interactions between the core region and the environment, as well as for nonelectrostatic (also known as Pauli and exchange) repulsion. All environmental effects are included through one-electron operators and account very efficiently for the response of the environment due to the change in the electron density of the core region, e.g., upon an electronic transition.
我们介绍了可极化密度嵌入（PDE）模型与耦合簇（CC）理论（PDE - CC）相结合的理论及实现方法。该模型已通过将CC代码适配到可极化嵌入库（PElib），在Dalton量子化学程序中得以实现。在PDE - CC方法中，较小但化学性质重要的核心区域采用高级CC方法进行描述。核心区域周围的环境可分为两个描述层次：内层区域和外层区域。内层区域对核心区域的影响通过一个嵌入势来描述，该嵌入势由一组片段密度组成，这些片段密度是通过诸如Hartree - Fock（HF）或Kohn - Sham密度泛函理论（KS - DFT）等量子化学方法对孤立片段进行计算得到的，并配以一组以原子为中心的各向异性偶极 - 偶极极化率。外层区域由分布在原子中心的多极矩和极化率组成，即与可极化嵌入（PE）模型中的方式相同。PDE - CC方法包含嵌入势算符，用于考虑核心区域与环境之间的静电和极化相互作用，以及非静电（也称为泡利和交换）排斥作用。所有环境效应都通过单电子算符纳入，并且能非常有效地考虑由于核心区域电子密度变化（例如在电子跃迁时）导致的环境响应。
