Abstract
In explicitly correlated coupled-cluster singles and doubles [CCSD(F12)] calculations, the basis set incompleteness error in the double excitations is reduced to such an extent that the error in the Hartree-Fock energy and the error in the single excitations become important. Using arguments from perturbation theory to systematically truncate the coupled-cluster singles and CCSD(F12) Lagrangians, a series of coupled-cluster models are proposed and studied that reduce these basis set incompleteness errors through additional single excitations into a complementary auxiliary basis. Convergence with model and size of complementary basis is rapid and there appears to be no need to go beyond second-order models. Our iterative second-order approach is a slight improvement over the existing noniterative approach, but its main advantage is that it is suitable for response theory.
Original language | English |
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Article number | 024101 |
Number of pages | 10 |
Journal | Journal of Chemical Physics |
Volume | 132 |
Issue number | 2 |
DOIs | |
Publication status | Published - 14 Jan 2010 |
Keywords
- coupled cluster calculations
- excited states
- HF calculations
- perturbation theory
- CORRELATED PERTURBATION-THEORY
- MOLLER-PLESSET CALCULATIONS
- ELECTRONIC-STRUCTURE THEORY
- ZETA BASIS-SETS
- DUAL BASIS-SETS
- NUMERICAL QUADRATURES
- CORRELATION ENERGIES
- CORRELATION CUSP
- WAVE-FUNCTIONS
- ERRORS