Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
J Chem Phys. 2010 Aug 14;133(6):061102. doi: 10.1063/1.3470106.
The constrained density functional theory-configuration interaction (CDFT-CI) method has previously been used to calculate ground-state energies and barrier heights. In this work, it is examined for use in computing electronic excited states, for the challenging case of conical intersections. Conical intersections are a prevalent feature of excited electronic surfaces, but conventional time-dependent density functional theory calculations are found to be entirely unsatisfactory at describing them, for two small systems. CDFT-CI calculations on those systems are found to be in qualitative agreement with reference CAS surfaces. These results suggest that with a suitable definition of atomic populations and a careful choice of constrained states, CDFT-CI could be the basis for a seamless description of electronic degeneracy.
约束密度泛函理论-组态相互作用（CDFT-CI）方法之前已被用于计算基态能量和势垒高度。在这项工作中，研究了它在计算电子激发态方面的应用，特别是在圆锥交叉点的挑战性情况下。圆锥交叉点是激发电子表面的一个普遍特征，但对于两个小系统，传统的含时密度泛函理论计算完全无法描述它们。对这些系统的 CDFT-CI 计算发现与参考 CAS 表面定性一致。这些结果表明，通过适当定义原子布居和仔细选择约束态，CDFT-CI 可以成为电子简并的无缝描述的基础。
