Full-dimensional quantum dynamics study of the H2 + C2H → H + C2H2 reaction on an ab initio potential energy surface

Abstract

This work performs a time-dependent wavepacket study of the H2 + C2H → H + C2H2 reaction on a new ab initio potential energy surface (PES). The PES is constructed using neural network method based on 68 478 geometries with energies calculated at UCCSD(T)-F12a/aug-cc-pVTZ level and covers H2 + C2H↔H + C2H2, H + C2H2 → HCCH2, and HCCH2 radial isomerization reaction regions. The reaction dynamics of H2 + C2H → H + C2H2 are investigated using full-dimensional quantum dynamics method. The initial-state selected reaction probabilities are calculated for reactants in eight vibrational states. The calculated results showed that the H2 vibrational excitation predominantly enhances the reactivity while the excitation of bending mode of C2H slightly inhibits the reaction. The excitations of two stretching modes of C2H molecule have negligible effect on the reactivity. The integral cross section is calculated with J-shift approximation and the mode selectivity in this reaction is discussed. The rate constants over 200-2000 K are calculated and agree well with the experimental measured values.

The ionization energy of the vinyl radical: a Mexican standoff with a happy ending

“…Experimental and theoretical studies on the tunneling splitting found that the minima are connected by a straight Y-shaped C2v transition state, [2] ‡ , along the CCH bending mode. The electronic energy of this transition state has been reported to be about 0.21 eV above that of the global minimum in various experimental 8,9 and computational [10][11][12][13][14] works. After years of quantum chemical research, a consensus has emerged that, similarly to the ethyl cation, 15 the vinyl cation also has a non-classical C2v global minimum with a proton bridging the two carbon atoms, [3] + .…”

An exact variational method to calculate rovibrational spectra of polyatomic molecules with large amplitude motion

“…By using the recent ab initio potential energy surface of Chen et al, 89 we have accuately calculated the lowest hundreds of rovibrational states of C 2 H 3 . The results will be published elsewhere.…”

Recent advances in quantum scattering calculations on polyatomic bimolecular reactions

“…were investigated using the full-dimensional ISSWP method on a new ab initio PES 197 . This PES was constructed using neural network method based on roughly 70 000 data points calculated at UCCSD(T)-F12a/AVTZ level and covers H2+C2H ↔ H+C2H2, H+C2H2 → HCCH2, and HCCH2 radial isomerization reaction regions.…”