Accurate ab-initio computation of thermochemical data for C{sub 3}H{sub x} (x=0,...,4) species.

Journal Article · Tue Jan 01 04:00:00 EST 2008 · J. Chem. Phys.

OSTI ID:968961

Aguilera-Iparraguire, J; Boese, A D; Klopper, W; Ruscic, B; Karlsruhe, Forschungszentrum

We have computed the atomization energies of nineteen C{sub 3}H{sub x} molecules and radicals using explicitly-correlated coupled-cluster theory including corrections for core-core and core-valence correlation, scalar and spin-orbit relativistic effects, and anharmonic vibrational zero-point energies. Equilibrium geometries were obtained at the coupled-cluster level [CCSD(T) model] in a correlation-consistent polarized core-valence quadruple-zeta basis set, using a spin-restricted Hartree-Fock reference wave function, and including all electrons in the correlation treatment. Applied to a set of selected CH{sub x} and C{sub 2}H{sub x} systems, our approach yields highly accurate atomization energies with a mean absolute deviation of 1.4 kJ/mol and a maximum deviation of 4.2 kJ/mol (for dicarbon) from the Active Thermochemical Tables (ATcT) values. The explicitly-correlated coupled-cluster approach provides energies near the basis-set limit of the CCSD(T) model, which is the coupled-cluster model with single and double excitations (CCSD) augmented with a perturbative correction for triple excitations (T). To obtain even more accurate atomization energies than those presented here, it would be required to include full triple excitations (CCSDT) and corrections for excitations beyond triples, as for instance done in the CCSDT(Q) model, which includes a perturbative correction for quadruple excitations (Q).

• Research Organization: Argonne National Laboratory (ANL)
• Sponsoring Organization: SC; Deutsche Forschungsgemeinschaft; Fonds der Chemischen Industrie
• DOE Contract Number: AC02-06CH11357
• OSTI ID: 968961
• Report Number(s): ANL/CSE/JA-60595
• Journal Information: J. Chem. Phys., Journal Name: J. Chem. Phys. Journal Issue: 2008 Vol. 346; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ATOMIZATION
RADICALS
THERMOCHEMICAL PROCESSES
WAVE FUNCTIONS