Interference-corrected explicitly correlated second-order perturbation theory (INT-MP2-F12) is applied to accelerate the convergence to the completebasis- set limit of coupled-cluster computations. Adding energy terms obtained from INT-MP2-F12 theory to the energies obtained from coupled-cluster singles-and-doubles (CCSD) computations yields a mean absolute deviation (MAD) from explicitly correlated CCSD results below 1 kJ/mol for a test set of 106 molecules. A composite scheme for the computation of atomization energies is assessed. This scheme is denoted as CCSD(T)+F12+INT and consists of the CCSD model with perturbative triples (CCSD(T)) supplemented with INT-MP2-F12 corrections, using a quadruple-zeta quality basis set (cc-pVQZ-F12). The composite scheme achieves chemical accuracy with respect to experimentally derived or computed reference values. Using Boys localized molecular orbitals, the MAD of the CCSD(T)+F12+INT/cc-pVQZ-F12 atomization energies from the reference values is below 1 kJ/mol for the G2/97 test set.
Bibliographical noteFunding Information:
This work was supported by the DFG through the Center for Functional Nanostructures (CFN, Project No. C3.3). We are also grateful to the Bundesministerium für Bildung und Forschung (BMBF) through the Helmholtz Research Programme “Science and Technology of Nanosystems” and to the State of Baden-Württemberg for providing the necessary infrastructure. R.H. thanks the Carl-Zeiss-Stiftung for financial support.
- Atomization energy
- Coupled-cluster theory
- Explicit correlation
- Interference effects
- Performance assessment
- Test set