Accurate Bond Energies of Hydrocarbons from Complete Basis Set Extrapolated Multi-Reference Singles and Doubles Configuration Interaction

• Published in: Chemphyschem 2011-12, Vol.12 (17), p.3354-3364
• Main Authors: Oyeyemi, Victor B., Pavone, Michele, Carter, Emily A.
• Format: Article
• Language: English
• Subjects: Ab initio calculations; ACCURACY; Atomic and molecular physics; bond dissociation; Calculations and mathematical techniques in atomic and molecular physics (excluding electron correlation calculations); CHEMISTRY; CLUSTER EXPANSION; CONFIGURATION INTERACTION; Density-functional theory; DISSOCIATION; ELECTRON CORRELATION; Electronic structure of atoms, molecules and their ions: theory; Environmental Molecular Sciences Laboratory; Exact sciences and technology; EXCITATION; FORECASTING; HYDROCARBONS; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; multi-reference configuration interaction; Physics; thermochemistry; WAVE FUNCTIONS
• ISSN: 1439-4235; 1439-7641
• DOI: 10.1002/cphc.201100447

Quantum chemistry has become one of the most reliable tools for characterizing the thermochemical underpinnings of reactions, such as bond dissociation energies (BDEs). The accurate prediction of these particular properties (BDEs) are challenging for ab initio methods based on perturbative corrections or coupled cluster expansions of the single‐determinant Hartree–Fock wave function: the processes of bond breaking and forming are inherently multi‐configurational and require an accurate description of non‐dynamical electron correlation. To this end, we present a systematic ab initio approach for computing BDEs that is based on three components: 1) multi‐reference single and double excitation configuration interaction (MRSDCI) for the electronic energies; 2) a two‐parameter scheme for extrapolating MRSDCI energies to the complete basis set limit; and 3) DFT‐B3LYP calculations of minimum‐energy structures and vibrational frequencies to account for zero point energy and thermal corrections. We validated our methodology against a set of reliable experimental BDE values of CC and CH bonds of hydrocarbons. The goal of chemical accuracy is achieved, on average, without applying any empirical corrections to the MRSDCI electronic energies. We then use this composite scheme to make predictions of BDEs in a large number of hydrocarbon molecules for which there are no experimental data, so as to provide needed thermochemical estimates for fuel molecules. On target: A proposed ab initio composite approach based on complete basis set extrapolated multi‐reference single‐ and double‐excitation configuration interaction predicts hydrocarbon bond dissociation energies within “chemical accuracy” without resorting to empirical corrections (see picture).