标题： 使用DMRG参考波函数的外部收缩多参考组态相互作用方法 显示英文标题

标题： Externally-Contracted Multi-Reference Configuration Interaction Method Using a DMRG Reference Wave Function

摘要： 最近在多参考量子化学中的密度矩阵重正化群（DMRG）方法的发展，使得在大的活性空间中评估静态关联成为可能，而动态关联对强关联系统的DMRG参考态提供关键修正，通常使用带有内部收缩（ic）近似的多参考微扰（MRPT）或组态相互作用（MRCI）方法获得。 这些方法可以使用比以前可能更大的活性空间的参考态。 然而，由于高阶约化密度矩阵（RDMs）的计算和存储成本很高，且虚拟轨道的数量通常限制在几百个以内，它们仍然难以应用于活性空间超过30个轨道的系统。 在本工作中，我们提出了一种新的DMRG-MRCI有效实现方式，其中我们通过熵驱动遗传算法（EDGA）从DMRG波函数中重构出CASCI类型的组态，并通过外部收缩（ec）方案与MRCI结合。 这避开了传统DMRG动态关联方法中使用ic近似时计算高阶RDMs的瓶颈，且MRCI组态数量不依赖于虚拟轨道数量。 因此，DMRG-ec-MRCI方法有望处理比30个轨道更大的活性空间和大基组。 我们在几个基准应用中展示了我们DMRG-ec-MRCI方法的能力，包括Cr$_{2}$的势能曲线评估、更高n-烯烃分子的单重态-三重态间隙以及Eu-BTBP(NO$_3$)$_3$复合物的能量。 显示英文摘要

摘要： The recent development of the density matrix renormalization group (DMRG) method in multireference quantum chemistry makes it practical to evaluate static correlation in a large active space, while dynamic correlation provides a critical correction to the DMRG reference for strong-correlated systems and is usually obtained using multi-reference perturbation (MRPT) or configuration interaction (MRCI) methods with internal contraction (ic) approximation. These methods can use active space scalable to relatively larger size references than has previously been possible. However, they are still hardly applicable to systems with active space larger than 30 orbitals because of high computation and storage costs of high-order reduced density matrices (RDMs) and the number of virtual orbitals are normally limited to few hundreds. In this work, we propose a new effective implementation of DMRG-MRCI, in which we use re-constructed CASCI-type configurations from DMRG wave function via the entropy-driving genetic algorithm (EDGA), and integrate with MRCI by an external contraction (ec) scheme. This bypasses the bottleneck of computing high-order RDMs in traditional DMRG dynamic correlation methods with ic approximation and the number of MRCI configurations is not dependent on the number of virtual orbitals. Therefore, DMRG-ec-MRCI method is promising for dealing with larger active space than 30 orbitals and large basis sets. We demonstrate the capability of our DMRG-ec-MRCI method in several benchmark applications, including the evaluation of potential energy curve of Cr$_{2}$, single-triplet gaps of higher n-acene molecules and the energy of Eu-BTBP(NO$_3$)$_3$ complex.