Department of Chemistry, Chemical Theory Center, and Minnesota Supercomputing Institute , University of Minnesota , Minneapolis , Minnesota 55455-0431 , United States.
J Chem Theory Comput. 2018 Apr 10;14(4):1960-1968. doi: 10.1021/acs.jctc.7b01248. Epub 2018 Mar 13.
Density matrix embedding theory (DMET) [ Phys. Rev. Lett. 2012, 109, 186404] has been demonstrated as an efficient wave-function-based embedding method to treat extended systems. Despite its success in many quantum lattice models, the extension of DMET to real chemical systems has been tested only on selected cases. Herein, we introduce the use of the complete active space self-consistent field (CASSCF) method as a correlated impurity solver for DMET, leading to a method called CAS-DMET. We test its performance in describing the dissociation of H-H single bonds in a H ring model system and an N═N double bond in azomethane (CH-N═N-CH) and pentyldiazene (CH(CH)-N═NH). We find that the performance of CAS-DMET is comparable to CASSCF with different active space choices when single-embedding DMET corresponding to only one embedding problem for the system is used. When multiple embedding problems are used for the system, the CAS-DMET is in good agreement with CASSCF for the geometries around the equilibrium, but not in equal agreement at bond dissociation.
密度矩阵嵌入理论（DMET）[Phys. Rev. Lett. 2012, 109, 186404]已被证明是一种有效的基于波函数的嵌入方法，可用于处理扩展系统。尽管它在许多量子格子模型中取得了成功，但 DMET 的扩展到真实的化学系统仅在选定的情况下进行了测试。在此，我们引入了将完全活性空间自洽场（CASSCF）方法用作 DMET 的相关杂质求解器的方法，称为 CAS-DMET。我们测试了它在描述 H 环模型系统中的 H-H 单键和偶氮甲烷（CH-N═N-CH）和戊二氮（CH(CH)-N═NH）中的 N═N 双键的解离中的性能。我们发现，当仅使用对应于系统的一个嵌入问题的单嵌入 DMET 时，CAS-DMET 的性能与具有不同活性空间选择的 CASSCF 相当。当系统使用多个嵌入问题时，对于平衡附近的几何形状，CAS-DMET 与 CASSCF 一致，但在键解离处不一致。
