Reference dependence of the two-determinant coupled-cluster method for triplet and open-shell singlet states of biradical molecules
Abstract
We study the performance of the two-determinant (TD) coupled-cluster (CC) method which, unlike conventional ground-state single-reference (SR) CC methods, can, in principle, provide a naturally spin-adapted treatment of the lowest-lying open-shell singlet (OSS) and triplet electronic states. Various choices for the TD-CC reference orbitals are considered, including those generated by the multi-configurational self-consistent field method. Comparisons are made with the results of high-level SR-CC, equation-of-motion (EOM) CC, and multi-reference EOM calculations performed on a large test set of over 100 molecules with low-lying OSS states. It is shown that in cases where the EOMCC reference function is poorly described, TD-CC can provide a significantly better quantitative description of OSS total energies and OSS-triplet splittings.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Apr 24, 2018
- Source ID
- 10.1063/1.5025170
Entities
People
- Ajith Perera
- Jesse J Lutz
- Marcel Nooijen
- Rodney J. Bartlett
Organizations
- Air Force Institute of Technology
- Engineer Research and Development Center
- Oak Ridge Associated Universities
- University of Florida
- University of Waterloo