Interaction of CH4 with Electronically Excited O2: Ab Initio Potential Energy Surfaces and Reaction Kinetics

Reaction of the N Atom with Electronically Excited O2 Revisited: A Theoretical Study

“…To additionally verify the accuracy of calculated values of E a + (a) and E a + (b) energy barriers, the compound G3MP2, G4MP2, and CBS-QB3 methods, based on a sequence of predefined ab initio molecular orbital calculations and involving special empirical corrections to ensure high target accuracy, were employed. Note that these composite techniques were chosen for comparative analysis because they had previously been proved to be effective in determining energy barriers on the excited PESs. ,,,, …”

“…Note that these composite techniques were chosen for comparative analysis because they had previously been proved to be effective in determining energy barriers on the excited PESs. 94,108,109,153,154 One can see that the use of modern higher-level methods in general leads to some decrease in the entrance energy barriers on the 2 A′ and 4 A′ PESs compared with early data by Walch and Jaffe. 17 with CASPT2 calculations 37 giving the lowest E a + (a) value [aside from the zero value obtained by Starik et al 44 during the plain CASSCF calculations with apparently insufficient (9,7) active space].…”

“…To this end, we applied a simple semiempirical model based on the computed harmonic vibrational frequencies and the reduced masses of respective modes, and the specific model parameters optimized to describe the Morse anharmonicity of the species containing N, O, and H atoms were used. Note that this variant of AHO approximation, despite some simplifying assumptions made, such as neglecting the quartic vibrational anharmonicity and mode–mode coupling, shows a tolerable accuracy not only for reactants and TSs involved in chemical reactions ,, but also for atomic clusters of different compositions …”

“…Dunning’s correlation consistent basis sets with diffuse functions aug-cc-pV X Z (maximum angular momentum quantum numbers X = 2...4) were applied throughout the present study. Note that the use of this general-purpose basis set family is usually sufficient to trace basis set convergence for the excited PESs of small and medium-sized reactive systems. ,,− For convenience, we shall call hereafter the overall ab initio model as XMCQDPT2­(11,9)/aug-cc-pV X Z. All electronic structure calculations were performed using the Firefly QC program package, which is partially based on the GAMESS (US) source code …”

Toward size-dependent thermodynamics of nanoparticles from quantum chemical calculations of small atomic clusters: a case study of (B2O3)n

“…Notice that this variant of AHO approximation, despite some simplifying assumptions made, such as neglecting the quartic vibrational anharmonicity and mode-mode coupling, shows a tolerable accuracy for polyatomic species of different elemental composition. 14,58,115–117…”