| Autor: |
Menéndez M; Departamento de Química Física, Unidad Asociada CSIC, Universidad Complutense de Madrid, 28040 Madrid, Spain. aoiz@ucm.es., Veselinova A; Departamento de Química Física, Universidad de Salamanca, 37008 Salamanca, Spain., Zanchet A; Instituto de Física Fundamental, CSIC, C/Serrano 121-123, 28006 Madrid, Spain., Jambrina PG; Departamento de Química Física, Universidad de Salamanca, 37008 Salamanca, Spain., Aoiz FJ; Departamento de Química Física, Unidad Asociada CSIC, Universidad Complutense de Madrid, 28040 Madrid, Spain. aoiz@ucm.es. |
| Abstrakt: |
We present here extensive calculations of the O( 3 P) + H 2 and O( 3 P) + D 2 reaction dynamics spanning the temperature range from 200 K to 2500 K. The calculations have been carried out using fully converged time-independent quantum mechanics (TI QM), quasiclassical trajectories (QCT) and ring polymer molecular dynamics (RPMD) on the two lowest lying adiabatic potential energy surfaces (PESs), 1 3 A' and 1 3 A'', calculated by Zanchet et al. [ J. Chem. Phys. , 2019, 151 , 094307]. TI QM rate coefficients were determined using the cumulative reaction probability formalism on each PES including all of the total angular momenta and the Coriolis coupling and can be considered to be essentially exact within the Born-Oppenheimer approximation. The agreement between the rate coefficients calculated by using QM and RPMD is excellent for the reaction with D 2 in almost the whole temperature range. For the reaction with H 2 , although the agreement is very good above 500 K, the deviations are significant at lower temperatures. In contrast, the QCT calculations largely underestimate the rate coefficients for the two isotopic variants due to their inability to account for tunelling. The differences found in the disagreements between RPMD and QM rate coefficients for the reactions for both the isotopologues are indicative of the ability of the RPMD method to accurately describe systems where tunelling plays a relevant role. Considering that both reactions are dominated by tunelling below 500 K, the present results show that RPMD is a very powerful tool for determining rate coefficients. The present QM rate coefficients calculated on adiabatic PESs slightly underestimate the best global fits of the experimental measurements, which we attribute to the intersystem crossing with the singlet 1 1 A' PES. |
