Can coupled cluster singles and doubles be approximated by a valence active space model?
A new, efficient approximation for coupled cluster singles and doubles (CCSD) is proposed in which CCSD calculation is performed in a valence active space followed by a second-order perturbative correction to account for the inactive singles and doubles cluster amplitudes. This method, denoted VCCSD(SD), satisfactorily reproduces CCSD results in a variety of test cases, including spectroscopic constants of diatomic molecules, reaction energies, the Cope rearrangement, and other relative energies. Use of VCCSD alone is significantly less satisfactory. Formally, the O2V4 scaling of CCSD is reduced to o2v2V2, where o is the number of active occupied orbitals, v is the number of active virtual orbitals, and V is the total number of virtual orbitals. We also investigate the role of orbital optimizations and the appropriate choice of an active space in such methods.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Director. Office of Science. Basic Energy Sciences. SciDAC Computational Chemistry Program Grant DE-FG02-01ER403301 (US)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 823067
- Report Number(s):
- LBNL-51046; JCPSA6; R&D Project: 403301; TRN: US200415%%153
- Journal Information:
- Journal of Chemical Physics, Vol. 117, Issue 7; Other Information: Journal Publication Date: 15 August 2002; PBD: 21 May 2002; ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
Similar Records
A Massively Parallel Implementation of the CCSD(T) Method Using the Resolution-of-the-Identity Approximation and a Hybrid Distributed/Shared Memory Parallelization Model
Coupled-cluster based basis sets for valence correlation calculations