基于完全活性空间自洽场的杂化多组态密度泛函方法λ-DFCAS

提出了一种杂化多组态密度泛函新方法——λ-DFCAS. 在λ-DFCAS方法中, 电子相关能被分为静态和动态相关能. 静态相关能由多组态波函数方法完全活性空间自洽场(CASSCF)得到, 而动态相关能由密度泛函理论方法描述. 两种相关能的杂化比例由一个可调节的参数λ控制. 参数λ的取值取决于分子体系的多组态特性, 在0~1之间变化, 从而使得λ-DFCAS可以应用于各种强相关分子体系. 该方法能够以与CASSCF相当的计算代价获得接近完全活性空间二阶微扰(CASPT2)的计算精度, 并具备了大小一致性.

λ-DFCAS： A Hybrid Density Functional Complete Active Space Self Consistent Field Method

A multireference density functional theory method， named λ-DFCAS， is presented in this paper. Based on the strategy used in λ-DFVB method， the λ-DFCAS method divides electronic correlation into two parts： the static correlation is covered by multi-reference wave function method， complete active space self-consistent field（CASSCF）， while the dynamic correlation is provided by Kohn-Sham density functional theory（KS-DFT）. The parameter λ in λ-DFCAS， controlling the hybrid extent of dynamic and static correlations， varies according to the multireference character of a given molecular system. The λ-DFCAS method provides a multireference density functional theory with size-consistency. Test examples show that the accuracy of λ-DFCAS is close to the complete active space second perturbation theory（CASPT2） method， while its computational cost is roughly the same as CASSCF.