Generalization of the Tensor Product Selected CI Method for Molecular Excited States
Generalization of the Tensor Product Selected CI Method for Molecular Excited States
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分子激发态张量积选择 CI 方法的推广
DOI：
10.1021/acs.jpca.3c03161
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Mayhall, Nicholas J.
中科院分区：
文献类型：
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作者：
Braunscheidel, Nicole M.;Abraham, Vibin;Mayhall, Nicholas J.
在最近的一篇论文[JCTC，2020，16，6098]中，我们介绍了一种新的方法，用于在大型电子活性空间中准确近似完整的CI基态，称为张量积选择CI（TPSCI）。在TPSCI中，一个大的轨道活动空间首先被划分成不相交的集合（集群），获得精确的，局部的多体本征态。这些局部相关的多体状态的张量积被视为完整的，全球性的希尔伯特空间的基础。通过将相关性折叠到基态本身，低能本征态变得越来越稀疏，从而产生更紧凑的选择CI展开。虽然我们证明了这种方法可以提高各种系统的精度，但对于激发态的应用，特别是那些具有激发态特征的应用，有更大的潜力。在本文中，我们报告TPSCI的激发态的准确性，包括更有效的实现在Julia编程语言。在使用斯莱特行列式基础的传统SCI方法中，仅在线性外推之后并且以大的计算成本获得准确的激发能。我们发现，TPSCI与微扰修正提供了准确的激发能的几个激发态的各种多环芳烃相对于外推的结果（即，近似精确的结果）。此外，我们使用TPSCI报告高度准确的估计最低的31个本征态的并四苯四聚体系统的40个电子在40个轨道的活性空间，直接访问初始亮态和由此产生的18个双激发（双激子）状态。
In a recent paper [JCTC,2020,16,6098], we introduced a new approach for accurately approximating full CI ground states in large electronic active-spaces called Tensor Product Selected CI (TPSCI). In TPSCI, a large orbital active space is first partitioned into disjoint sets (clusters) for which the exact, local many-body eigenstates are obtained. Tensor products of these locally correlated many-body states are taken as the basis for the full, global Hilbert space. By folding correlation into the basis states themselves, the low-energy eigenstates become increasingly sparse, creating a more compact selected CI expansion. While we demonstrated that this approach can improve accuracy for a variety of systems, there is even greater potential for applications to excited states, particularly those which have some excited-state character. In this paper, we report on the accuracy of TPSCI for excited states, including a far more efficient implementation in the Julia programming language. In traditional SCI methods that use a Slater determinant basis, accurate excitation energies are obtained only after a linear extrapolation and at a large computational cost. We find that TPSCI with perturbative corrections provides accurate excitation energies for several excited states of various polycyclic aromatic hydrocarbons with respect to the extrapolated result (i.e., near exact result). Further, we use TPSCI to report highly accurate estimates of the lowest 31 eigenstates for a tetracene tetramer system with an active space of 40 electrons in 40 orbitals, giving direct access to the initial bright states and the resulting 18 doubly excited (biexcitonic) states.