Transition moments and excited-state first-order properties in the coupled-cluster model CC2 using the resolution-of-the-identity approximation
Transition moments and excited-state first-order properties in the coupled-cluster model CC2 using the resolution-of-the-identity approximation
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DOI：
10.1063/1.1506918
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发表时间：
2002-10-15
影响因子：
4.4
通讯作者：
Köhn, A
中科院分区：
文献类型：
--
作者：
Hättig, C;Köhn, A
本文报道了利用单位近似（RI）的分辨率实现近似耦合簇单双模型（CC2）的跃迁矩和激发态一阶性质。与之前报道的基态和激发态振幅方程的代码并行，我们利用CC2方程的分区形式，从而消除了存储任何N-4中间体的需要。这为具有30个或更多原子的分子的应用打开了前景。对29个分子的aug-cc-pVXZ （X=D，T，Q）基集与最近优化的辅助基集进行了RI近似的准确性测试。这些辅助基集甚至对于描述扩散态也是充分的。将RI误差与通常的基集误差进行比较，并证明其不显著。(C) 2002年美国物理研究所。
An implementation of transition moments and excited-state first-order properties is reported for the approximate coupled-cluster singles-and-doubles model (CC2) using the resolution of the identity (RI) approximation. In parallel to the previously reported code for the ground- and excited-state amplitude equations, we utilize a partitioned form of the CC2 equations and thus eliminate the need to store any N-4 intermediates. This opens the perspective for applications on molecules with 30 and more atoms. The accuracy of the RI approximation is tested for a set of 29 molecules for the aug-cc-pVXZ (X=D,T,Q) basis sets in connection with the recently optimized auxiliary basis sets. These auxiliary basis sets are found to be sufficient even for the description of diffuse states. The RI error is compared to the usual basis set error and is demonstrated to be insignificant. (C) 2002 American Institute of Physics.