We report the implementation of the Laplace-transform scaled opposite-spin (LT-SOS) resolution-of-the-identity second-order approximate coupled-cluster singles and doubles (RICC2) combined with frozen-density embedding for excitation energies and molecular properties. In the present work, we furthermore employ the Hartree-Fock density for the interaction energy leading to a simplified Lagrangian which is linear in the Lagrangian multipliers. This approximation has the key advantage of a decoupling of the coupled-cluster amplitude and multipliers, leading also to a significant reduction in computation time. Using the new simplified Lagrangian in combination with efficient wavefunction models such as RICC2 or LT-SOS-RICC2 and density-functional theory (DFT) for the environment molecules (CC2–in–DFT) enables the efficient study of biological applications such as the rhodopsin and visual cone pigments using ab initio methods as routine applications.

中文翻译：

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交流：耦合簇冻结密度嵌入的生物学应用

我们报告了Laplace变换缩放的反向自旋（LT-SOS）的恒等式二阶近似耦合集群单打和双打（RICC2）结合冻结密度嵌入的激发能和分子性质的实现。在目前的工作中，我们还采用了Hartree-Fock密度作为相互作用能，从而得到了一个简化的拉格朗日数，该拉格朗日数在拉格朗日乘数中是线性的。这种近似的主要优点是，耦合群集的振幅和乘法器解耦，从而也大大减少了计算时间。从头算方法作为常规应用程序。