Institute of Chemistry, University of Silesia, Szkolna 9, 40-006 Katowice, Poland.
J Chem Phys. 2009 Nov 21;131(19):194104. doi: 10.1063/1.3265770.
The role of connected triple excitations in coupled cluster (CC) calculations of vertical excitation energies, ionization potentials, and the electron affinity of the ozone molecule is evaluated. The equation of motion (EOM) and Fock space (FS) multireference CC approaches with full triples have been used in the calculations. The effect of the T(3) and R(3) operators significantly improve the EOM CCSD results for all considered quantities. A similar behavior is observed in the case of the FS-CC calculations. The FS-CC calculations with full triples have been obtained only for the intermediate Hamiltonian realization of the FS approach as the standard formulation diverges. The latter results are rigorously linked, and less expensive since smaller matrices are diagonalized.
本文评估了关联三重激发在垂直激发能、电离势和臭氧分子电子亲和能的耦合簇（CC）计算中的作用。在计算中使用了含完全三重项的运动方程（EOM）和 Fock 空间（FS）多参考 CC 方法。T(3)和 R(3)算符的作用显著提高了所有考虑的量的 EOM CCSD 结果。在 FS-CC 计算中也观察到了类似的行为。只有在 FS 方法的中间哈密顿量实现的情况下才能得到含完全三重项的 FS-CC 计算，因为标准公式发散。后者的结果是严格关联的，并且成本更低，因为较小的矩阵需要对角化。
