Modelling one- and two-photon spectroscopy in solution with the coupled-cluster model CC2 combined with continuum and atomistic embedding models

该项目的目的是为耦合簇方法CC2和相关的ADC(2)、CIS（Dinf）和CIS(D)方法（包括其自旋分量缩放的SCS和SOS变体）开发一种有效和通用的类导体筛选模型（COSMO）和原子极化嵌入模型（PE）。对于实现，我们将利用这两种方法都是自一致反应场模型的特殊情况，并且可以转换为公共工作流程和程序结构。在这两种方法中，电子与环境之间的相互作用都是通过嵌入或反应场势来描述的，它是一个单电子算子，是量子系统中电子密度的函数。在这两种情况下，作为对外部施加电磁场的响应，嵌入电位随量子系统变化的变化都应包括在内。对于像COSMO这样的连续溶剂化模型，参考文献显示了这一点。[1,2]。对于PE模型，对嵌入电位的响应贡献已经通过构造包含在其原始公式[3]中。嵌入电位的单电子形式及其对密度的依赖关系和对微扰的响应决定了嵌入电子结构计算的算法和工作流程。除了一光子和双光子UV/Vis跃迁的垂直激发能和强度外，还应包括一光子和双光子圆二色性的旋转强度，磷光寿命，以及电子基态和激发态的一、二、三阶性质和梯度。它应该集成到MPI和OpenMP并行版本中，以便在分布式和共享内存计算机系统上使用。应该删除已经存在的程序部分对闭壳Hartree-Fock引用的限制。为了验证这两种嵌入方法，需要编制一个包含实验和理论参考数据的测试集，并对COSMO和PE嵌入模型与相关波函数方法CC2、ADC(2)、CIS（Dinf）和CIS(D)的相互作用性能进行基准测试。

The aim of the project is the development of an efficient and general implementation of the Conductor-like screening model (COSMO) and the atomistic polarizable embedding model (PE) for the coupled-cluster method CC2 and the related ADC(2), CIS(Dinf) and CIS(D) methods including their spin-component scaled SCS and SOS variants. For the implementation we will exploit that both approaches are special cases of a self-consistent reaction field model and can be casted into a common work flow and program structure. In both approaches the interaction between the electrons and the environment is described through an embedding or reaction field potential which is a one-electron operator and a functional of the electron density in the quantum system. In both cases the changes of the embedding potential upon changes in the quantum system as response to an externally applied electromagnetic field should be included. For continuum solvation models like COSMO this was shown in Refs. [1,2]. For the PE model the response contributions to the embedding potential were already included by construction in its original formulation [3].The one-electron form of the embedding potential and its dependence on the density and its response to perturbations determines the algorithms and the workflow of the embedded electronic structure calculation. The implementation should comprise in addition to vertical excitation energies and intensities for one- and two-photon UV/Vis transitions also rotatory strengths for one- and two-photon circular dichroism, phosphorescence lifetimes, and first-, second- and third-order properties and gradients in the electronic ground and in excited states. It should be integrated into the MPI and OpenMP parallel versions for use on distributed and shared memory computer systems. The limitations of already existing program parts to closed-shell Hartree-Fock references should be removed.To validate the two embedding approaches, a test set with experimental and theoretical reference data should be compiled and the performance of the COSMO and PE embedding models in the interplay with the correlated wavefunction methods CC2, ADC(2), CIS(Dinf), and CIS(D) benchmarked for the implemented properties.