Tailored coupled cluster theory in varying correlation regimes.
Tailored coupled cluster theory in varying correlation regimes.
复制标题
不同相关机制下的定制耦合簇理论。
DOI：
10.1063/5.0032661
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
M. Reiher
中科院分区：
文献类型：
--
作者：
Maximilian Mörchen;Leon Freitag;M. Reiher
定制耦合簇（TCC）方法是一种有前途的模拟，它保留了单参考耦合簇理论的简单性，同时通过从先前的多配置计算获得的幅度合并了多参考波函数。在这里，我们基于模型系统对 TCC 波函数进行了详细分析，这需要准确描述静态和动态相关性。我们研究了 TCC 方法在精确波函数方面的可靠性。除了电子能量和标准耦合簇诊断中的误差之外，我们还利用 TCC 和全配置相互作用波函数的重叠作为质量度量。我们批判性地审查了一些问题，例如活动空间所需的尺寸、尺寸一致性、波函数的对称性破缺以及 TCC 对参考波函数的依赖性。我们观察到，通过使用活动空间中权重最大的行列式作为 TCC 计算的参考，可以减轻由对称性破缺引起的可能误差。我们发现 TCC 模型在包含具有大单轨道熵的所有轨道的活动轨道空间的计算中很有前景，即使活动空间变得非常大，然后可能需要不限于相对较少数量的轨道的现代活动空间方法。此外，利用大的活动空间可以改进TCC波函数近似并减少尺寸一致性误差，因为高激发行列式的存在会影响活动空间中低激发行列式的系数的准确性。
The tailored coupled cluster (TCC) approach is a promising ansatz that preserves the simplicity of single-reference coupled cluster theory while incorporating a multi-reference wave function through amplitudes obtained from a preceding multi-configurational calculation. Here, we present a detailed analysis of the TCC wave function based on model systems, which require an accurate description of both static and dynamic correlation. We investigate the reliability of the TCC approach with respect to the exact wave function. In addition to the error in the electronic energy and standard coupled cluster diagnostics, we exploit the overlap of TCC and full configuration interaction wave functions as a quality measure. We critically review issues, such as the required size of the active space, size-consistency, symmetry breaking in the wave function, and the dependence of TCC on the reference wave function. We observe that possible errors caused by symmetry breaking can be mitigated by employing the determinant with the largest weight in the active space as reference for the TCC calculation. We find the TCC model to be promising in calculations with active orbital spaces which include all orbitals with a large single-orbital entropy, even if the active spaces become very large and then may require modern active-space approaches that are not restricted to comparatively small numbers of orbitals. Furthermore, utilizing large active spaces can improve on the TCC wave function approximation and reduce the size-consistency error because the presence of highly excited determinants affects the accuracy of the coefficients of low-excited determinants in the active space.
影响因子：
2.2
作者：
Szilárd Szalay;Max Pfeffer;V. Murg;Gergely Barcza;F. Verstraete;R. Schneider;O. Legeza
通讯作者：
Szilárd Szalay;Max Pfeffer;V. Murg;Gergely Barcza;F. Verstraete;R. Schneider;O. Legeza