Atomization energies from coupled-cluster calculations augmented with explicitly-correlated perturbation theory.

Journal Article · Mon Nov 17 04:00:00 EST 2008 · Chem. Phys.

DOI:https://doi.org/10.1016/j.chemphys.2008.11.013· OSTI ID:990156

Klopper, W; Ruscic, B; Tew, D P; Bischoff, F A; Wolfsegger, S

The atomization energies of the 105 molecules in the test set of Bakowies [D. Bakowies, J. Chem. Phys. 127 (2007) 084105] have been computed with an estimated standard deviation (from the values compiled in the Active Thermochemical Tables) of {+-}0.1 kJ/mol per valence electron in the molecule. Equilibrium geometries and harmonic vibrational frequencies were calculated at the all-electron CCSD(T)/cc-pCVTZ level, that is, at the level of coupled-cluster theory with singles, doubles and non-iterative triples in a correlation-consistent polarized core-valence triple-zeta basis. Single-point energy calculations were performed at the all-electron CCSD(T) level in a correlation-consistent polarized core-valence quadruple-zeta basis (cc-pCVQZ), and several corrections were added: (i) a correction for the basis-set truncation error, obtained from second-order perturbation theory using Slater-type geminals (MP2-F12 theory), (ii) a correction for the effect of anharmonicity on the zero-point vibrational energy, (iii) a relativistic correction, (iv) a correction for the difference between the full CCSDT model (coupled-cluster theory with singles, doubles and triples) and the CCSD(T) approximation, and (v) a correction for connected quadruple excitations obtained from CCSDT(Q) calculations. The correction for the basis-set truncation error was obtained from MP2-F12 calculations by scaling the MP2 basis-set truncation error by an empirically optimized 'interference factor' of f{sub int} = 0.78. The reference values from the Active Thermochemical Tables for 73 molecules in the test set, the equilibrium geometries, the harmonic vibrational frequencies, and all of the energy corrections represent valuable data for performance assessments of additivity schemes that will be developed in the future, in which the basis-set truncation error will be calculated at the level of coupled-cluster theory using Slater-type geminals (CC-F12 theory). Such a scheme will be free of empirical corrections and scaling factors.

• Research Organization: Argonne National Laboratory (ANL)
• Sponsoring Organization: SC; DFG grants; Fonds der Chemischen Industrie
• DOE Contract Number: AC02-06CH11357
• OSTI ID: 990156
• Report Number(s): ANL/CSE/JA-62405
• Journal Information: Chem. Phys., Journal Name: Chem. Phys. Journal Issue: 11/17/2008 Vol. 356; ISSN 0301-0104
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ATOMIZATION
ELECTRONS
HARMONICS
PERFORMANCE
PERTURBATION THEORY
VALENCE