基于重复随机稀疏化子空间迭代的大活性空间全组态相互作用激发态能量
Full Configuration Interaction Excited-State Energies in Large Active Spaces from Subspace Iteration with Repeated Random Sparsification
AI总结：
本文提出基于FCI-FRI的非对称子空间迭代QMC方法，用试验向量保持正交并估计激发态能量，在多个大活性空间强关联分子上达到亚毫Hartree总能量和约0.1 eV激发能精度。
摘要：
我们提出了一种稳定且可系统改进的量子蒙特卡洛（QMC）方法，用于计算激发态能量，并使用我们针对全组态相互作用问题的快速随机迭代方法（FCI-FRI）加以实现。与以往的激发态量子蒙特卡洛方法不同，我们的方法是子空间迭代的一种非对称变体，避免使用随机向量的点积，而是依赖试验向量来维持正交性并估计本征值。利用近期进展，我们将该方法应用于计算大活性空间中强关联分子体系的基态和激发态能量，包括含8个电子、108个轨道（8e,108o）的碳二聚体，oxo-Mn(salen)过渡金属配合物（28e,28o），臭氧（18e,87o）和丁二烯（22e,82o）。在大多数测试案例中，我们的方法所得总激发态能量与热浴CI、密度矩阵重整化群方法和FCIQMC等最先进方法的结果相符，精度达到亚毫Hartree以内。在所有案例中，估计的激发能量均在约0.1 eV以内一致。
英文摘要：
We present a stable and systematically improvable quantum Monte Carlo (QMC) approach to calculating excited-state energies, which we implement using our fast randomized iteration method for the full configuration interaction problem (FCI-FRI). Unlike previous excited-state quantum Monte Carlo methods, our approach, which is an asymmetric variant of subspace iteration, avoids the use of dot products of random vectors and instead relies upon trial vectors to maintain orthogonality and estimate eigenvalues. By leveraging recent advances, we apply our method to calculate ground- and excited-state energies of strongly correlated molecular systems in large active spaces, including the carbon dimer with 8 electrons in 108 orbitals (8e,108o), an oxo-Mn(salen) transition metal complex (28e,28o), ozone (18e,87o), and butadiene (22e,82o). In the majority of these test cases, our approach yields total excited-state energies that agree with those from state-of-the-art methods -- including heat-bath CI, the density matrix renormalization group approach, and FCIQMC -- to within sub-milliHartree accuracy. In all cases, estimated excitation energies agree to within about 0.1 eV.
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