Cluster many-body expansion: A many-body expansion of the electron correlation energy about a cluster mean field reference
Cluster many-body expansion: A many-body expansion of the electron correlation energy about a cluster mean field reference
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DOI：
10.1063/5.0057752
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发表时间：
2021-08-07
影响因子：
4.4
通讯作者：
Mayhall, Nicholas J.
中科院分区：
文献类型：
--
作者：
Abraham, Vibin;Mayhall, Nicholas J.
多体展开（MBE）是一种计算相互作用能、结合能、晶格能等的有效工具，有着悠久的历史。在过去，MBE对关联能的应用在大型系统中是不可行的，但最近对计算资源的改进引发了人们对使用广义n阶Bethe-Goldstone方程捕获关联能的新兴趣。在这项工作中，我们将这种最初提出的用于斯莱特行列式的方法扩展到基于张量积态（TPS）的波函数。通过将活动空间划分为更小的轨道簇，我们的方法从簇平均场参考TPS配置开始，并使用MBE包含激发TPS的相关贡献。与直接从RHF参考中进行基于块的MBE相比，这种称为集群MBE （cMBE）的方法提高了低阶MBE的收敛性。我们提出了强相关系统的数值结果，如一维和二维哈伯德模型和铬二聚体。cMBE方法的性能还通过划分几个大型pi共轭系统的扩展pi空间来测试，包括具有114个轨道上114个电子的非常大的活性空间的石墨烯纳米片，这将需要10（66）个决定因素来获得精确的FCI解决方案。
The many-body expansion (MBE) is an efficient tool that has a long history of use for calculating interaction energies, binding energies, lattice energies, and so on. In the past, applications of MBE to correlation energy have been unfeasible for large systems, but recent improvements to computing resources have sparked renewed interest in capturing the correlation energy using the generalized nth order Bethe-Goldstone equation. In this work, we extend this approach, originally proposed for a Slater determinant, to a tensor product state (TPS) based wavefunction. By partitioning the active space into smaller orbital clusters, our approach starts from a cluster mean field reference TPS configuration and includes the correlation contribution of the excited TPSs using the MBE. This method, named cluster MBE (cMBE), improves the convergence of MBE at lower orders compared to directly doing a block-based MBE from a RHF reference. We present numerical results for strongly correlated systems, such as the one- and two-dimensional Hubbard models and the chromium dimer. The performance of the cMBE method is also tested by partitioning the extended pi space of several large pi-conjugated systems, including a graphene nano-sheet with a very large active space of 114 electrons in 114 orbitals, which would require 10(66) determinants for the exact FCI solution.