Rigorous close-coupling quantum dynamics calculation of thermal rate constants for the water formation reaction of H2 + OH on a high-level PES

Abstract

Thermal rate constants for the prototypical H 2 + OH → H + H 2 O reaction are calculated using quantum dynamics simulations including all degrees of freedom and accurately accounting for overall rotation via close-coupling. Results are reported for a recent, highly accurate neural network potential [J. Chen et al., J. Chem. Phys. 138, 154301 (2013)] and compared to results obtained on a previous, semi-empirical potential. Thermal rate constants between 300 K and 1000 K are reported and very good agreement with experimental work is found. Additionally, reasonable agreement for the closecoupling simulations on both potentials is found. In contrast to previous work, we find that the J-shifting approximation works well for the title reaction given that a high-level PES is used for the dynamics calculation. Moreover, the importance of treating the spin-orbit coupling in the reactant partition function is discussed. The highly accurate results reported here will provide a benchmark for the development of approximate methods. Published by AIP Publishing. https://doi

Low‐Temperature Thermal Rate Constants for the Water Formation Reaction H2+OH from Rigorous Quantum Dynamics Calculations

“…Accurate results on the NN1 and SE PESs are given as a black line and blue dots, respectively. Results from older work are given as gray long‐dashed line, and recent results as filled symbols …”

Low‐Temperature Thermal Rate Constants for the Water Formation Reaction H2+OH from Rigorous Quantum Dynamics Calculations

“…Accurate results on the NN1 and SE PESs are given as ab lack line and blue dots, respectively.Results from older work are given as gray long-dashed line, [34] and recent results as filled symbols. [38] Figure 3. CRPs compared to older work.…”

“…[30] Accurate,f ull-dimensional quantum dynamics calculations rigorously treating overall rotation with close coupling [31] or employing the J-shifting approximation [32][33][34][35] have been reported for the title reaction employing semi-empirical PESs. [36,37] However,o nly one study on the inaccurate,s emiempirical Schatz-Elgersma (SE) PES [34] reports TRCs below 300 K, down to 200 K. Very recently,the first accurate TRCs on am odern, high-level PES were published by the author, but these simulations were limited to temperatures above 300 K. [38] These calculations showed that the J-shifting approximation is valid for the NN1 PES [30] and that the older assessment of the inaccuracyo fJ -shifting for the title reaction is only true for the SE PES. [36] Accurate and efficient full-dimensional TRC calculations often employ the quantum transition-state concept [34,[39][40][41][42][43][44] as well as the multi-configurational time-dependent Hartree (MCTDH) approach.…”

“…Thed ifferences can be attributed to the inconsistent treatment of the spin-orbit splitting in the partition function calculation for the RPMD results. [38] TheN N1 PES was constructed without spin-orbit coupling.T hus the present work assumes that the true ground state is lowered by half the spin-orbit splitting.Y et, the RPMD simulations assume that the NN1 PES is the true,s pin-orbit-coupled ground state. This increases the rate constant by about afactor of two (see the Supporting Information and Ref.…”

An ab initio‐based global potential energy surface for the SH3 system and full‐dimensional state‐to‐state quantum dynamics study for the H2 + HS → H2S + H reaction

“…A number of ab initio ‐based global potential energy surfaces (PES) have been constructed for this reaction system . With the development of PES, fully converged integral cross sections (ICS), state‐to‐state differential cross sections (DCS), and quantum rate constants have been obtained. Excellent agreements were achieved for the first time for a four‐atom reaction between theory and high‐resolution crossed‐molecular beam experiment on DCS for the HD + OH → H 2 O + D reaction …”