TY - JOUR
T1 - Computational Study on the Mechanisms and Rate Constants for the O(3P,1D) + OCS Reactions
AU - Chen, Hsin Tsung
AU - Pham, Tien V.
AU - Lin, M. C.
PY - 2019/10/3
Y1 - 2019/10/3
N2 - The mechanisms and kinetics of O(3P,1D) + OCS(X1ς+) reactions have been studied by the high-level G2M(CC2) and CCSD(T)/6-311+G(3df)//B3LYP/6-311+G(3df) methods in conjunction with the transition-state theory and variational Rice-Ramsperger-Kassel-Marcus theory calculations. The result shows that the triplet surface proceeds directly by abstraction and substitution channels to produce SO(3P) + CO(X1ς+) and S(3P) + CO2(X1 ςg +) by passing the barriers of 7.6 and 9.1 kcal·mol-1 at the G2M(CC2)//B3LYP/6-311+G(3df) level, respectively, while two stable intermediates, LM1 (OSCO1) and LM2 (SC(O)O1), are formed barrierlessly from O(1D) + OCS(X1ς+) in the singlet surface, which lie at -40.5 and -50.1 kcal·mol-1 relative to O(3P) + OCS(X1ς+) reactants and decompose to CO(X1ς+) + SO(a1Δ) and S(1D) + CO2(X1ςg +). LM1 and LM2 may also be produced by singlet-triplet surface crossings via MSX1 and MSX2; the predicted total rate constant for the O(3P) + OCS(X1ς+) reaction including the crossings, 9.2 × 10-11 exp(-5.18 kcal·mol-1/RT) cm3 molecule-1 s-1, is in good agreement with available experimental data. The branching ratio of the CO2 product channel, 0.22-0.32, between 1200 and 1600 K, is also in excellent agreement with the value of 0.2-0.3 measured by Isshiki et al. (J. Phys. Chem. A. 2003, 107, 2464).
AB - The mechanisms and kinetics of O(3P,1D) + OCS(X1ς+) reactions have been studied by the high-level G2M(CC2) and CCSD(T)/6-311+G(3df)//B3LYP/6-311+G(3df) methods in conjunction with the transition-state theory and variational Rice-Ramsperger-Kassel-Marcus theory calculations. The result shows that the triplet surface proceeds directly by abstraction and substitution channels to produce SO(3P) + CO(X1ς+) and S(3P) + CO2(X1 ςg +) by passing the barriers of 7.6 and 9.1 kcal·mol-1 at the G2M(CC2)//B3LYP/6-311+G(3df) level, respectively, while two stable intermediates, LM1 (OSCO1) and LM2 (SC(O)O1), are formed barrierlessly from O(1D) + OCS(X1ς+) in the singlet surface, which lie at -40.5 and -50.1 kcal·mol-1 relative to O(3P) + OCS(X1ς+) reactants and decompose to CO(X1ς+) + SO(a1Δ) and S(1D) + CO2(X1ςg +). LM1 and LM2 may also be produced by singlet-triplet surface crossings via MSX1 and MSX2; the predicted total rate constant for the O(3P) + OCS(X1ς+) reaction including the crossings, 9.2 × 10-11 exp(-5.18 kcal·mol-1/RT) cm3 molecule-1 s-1, is in good agreement with available experimental data. The branching ratio of the CO2 product channel, 0.22-0.32, between 1200 and 1600 K, is also in excellent agreement with the value of 0.2-0.3 measured by Isshiki et al. (J. Phys. Chem. A. 2003, 107, 2464).
UR - http://www.scopus.com/inward/record.url?scp=85072904725&partnerID=8YFLogxK
U2 - 10.1021/acs.jpca.9b05720
DO - 10.1021/acs.jpca.9b05720
M3 - Article
C2 - 31469286
AN - SCOPUS:85072904725
SN - 1089-5639
VL - 123
SP - 8358
EP - 8364
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
IS - 39
ER -