title: The coupled cluster approach with a hybrid treatment of connected triple excitations based on the restricted Hartree-Fock reference.
abstract: A generalization of the coupled cluster (CC) singles, doubles, and a hybrid treatment of connected triples [denoted as CCSD(T)-h] [Shen et al., J. Chem. Phys. 132, 114115 (2010)] to the restricted Hartree-Fock (RHF) reference is presented. In this approach, active (or pseudoactive) RHF orbitals are constructed automatically by performing unitary transformations of canonical RHF orbitals so that they spatially mimic the natural orbitals of the unrestricted Hartree-Fock reference. The present RHF-based CCSD(T)-h approach has been applied to study the potential energy surfaces in several typical bond breaking processes and the singlet-triplet gaps in a diradical (HFH)(-1). For all systems under study, the overall performance of CCSD(T)-h is very close to that of the corresponding CCSD(T) (CC singles, doubles, and triples), and much better than that of CCSD(T) (CC singles, doubles, and perturbative triples).
authors.affiliation: Key Laboratory of Mesoscopic Chemistry of Ministry of Education, School of Chemistry and Chemical Engineering, Institute of Theoretical and Computational Chemistry, Nanjing University, Nanjing, 210093, People's Republic of China.
authors.forename: Jun
authors.initials: J
authors.lastname: Shen
authors.forename: Zhuangfei
authors.initials: Z
authors.lastname: Kou
authors.forename: Enhua
authors.initials: E
authors.lastname: Xu
authors.forename: Shuhua
authors.initials: S
authors.lastname: Li