论文标题
$ O（n^6）$扰动校正对相对旋转CCSD的显着准确性：对于耦合群集的化学精度是否需要三倍？
The remarkable accuracy of an $O(N^6)$ perturbative correction to opposite-spin CCSD: are triples necessary for chemical accuracy in coupled cluster?
论文作者
论文摘要
这项工作的重点是OS-CCSD-SPT（2），这是二阶相似性转化为扰动理论校正到相反的自旋耦合群集单打双打，在后者中，相同的自旋振幅被删除，并且相反的旋转幅度始终如一地解决。我们证明，对于非差异分子，OS-CCSD-SPT（2）产生的相对能量与CCSD（T）等高阶方法的准确性媲美。例如，在参考文献中使用PBE0轨道，OS-CCSD-SPT（2）相对于CCSD表现出0.66 kcal/mol的平均绝对偏差（MAD）（2）基准值W4-08雾化能量的非延期子集的基准值（C.F. MAD> 6 kcal/mol for CCSD）。 OS-CCSD-SPT（2）没有经验参数，具有$ O（n^6）$的器乐缩放，并且不使用三元组。它也自然地适合高阶校正：相关的三阶校正，确实涉及连接的三元组和四倍体的OS-CCSD-SPT（3），对同一基准表现出0.44 kcal/mol的MAD。
The focus of this work is OS-CCSD-SPT(2), which is a second-order similarity transformed perturbation theory correction to opposite spin coupled cluster singles doubles, where in the latter the same-spin amplitudes are removed and the opposite-spin ones are solved self consistently. We demonstrate that, for non-multireference molecules, OS-CCSD-SPT(2) produces relative energies that rival the accuracy of higher-order methods like CCSD(T). For example, using PBE0 orbitals in the reference, OS-CCSD-SPT(2) exhibits a mean absolute deviation (MAD) of 0.66 kcal/mol with respect to CCSD(2) benchmark values for the non-multireference subset of W4-08 atomization energies (c.f. a MAD > 6 kcal/mol for CCSD). OS-CCSD-SPT(2) is free of empirical parameters, has an instrinsic scaling of $O(N^6)$, and makes no use of triples. It is also naturally amenable to higher order corrections: the associated third-order correction, OS-CCSD-SPT(3), which does involve connected triples and quadruples, exhibits a MAD of 0.44 kcal/mol for the same benchmark.
