论文标题
单一参考统一多体理论中连接的三体术语：迭代和扰动近似
Connected three-body terms in single-reference unitary many-body theories: Iterative and perturbative approximations
论文作者
论文摘要
这项工作介绍了各种方法，将连接的三体术语包括在单一多体理论中，将代表性的示例集中在驱动的相似性重生群体（DSRG）上。从最小近似方法开始 - 线性化的DSRG截断为一体，二和三体操作员[LDSRG（3）] - 我们开发了几种近似LDSRG（3）模型，其计算成本降低。通过扰动分析，我们激励了一个迭代LDSRG（3） -$ n $和-n $（$ n = 1,2,3,4 $）的方法，其中包含LDSRG（3）图的子集。在这些变体中，LDSRG（3）-2方案具有与单打，双打和三倍（CCSDT）耦合群集理论相同的计算复杂性，但它在预测的相关能量的准确性下优于CCSDT。我们还基于将递归二次换向器增强的线性化DSRG提出并实施两个扰动三元校正[QDSRG（2）]。所得的QDSRG（2）+（t）方法与“金标准”耦合群集理论的准确性与单打，双打和扰动的三元模型在28个封闭壳原子和小分子的能量上相匹配。
This work introduces various approaches to include connected three-body terms in unitary many-body theories, focusing a representative example on the driven similarity renormalization group (DSRG). Starting from the least approximate method - the linearized DSRG truncated to one-, two-, and three-body operators [LDSRG(3)] - we develop several approximate LDSRG(3) models with reduced computational cost. Through a perturbative analysis, we motivate a family of iterative LDSRG(3)-$n$ and -$n'$ ($n=1,2,3,4$) methods that contain a subset of the LDSRG(3) diagrams. Among these variants, the LDSRG(3)-2 scheme has the same computational complexity of coupled cluster theory with singles, doubles, and triples (CCSDT), but it outperforms CCSDT in the accuracy of the predicted correlation energies. We also propose and implement two perturbative triples corrections based on the linearized DSRG truncated to one- and two-body operators augmented with recursive quadratic commutators [qDSRG(2)]. The resulting qDSRG(2)+(T) approach matches the accuracy of the "gold-standard" coupled cluster theory with singles, doubles, and perturbative triples model on the energetics of twenty-eight closed-shell atoms and small molecules.
