Browsing by Author "Xia, Wenwen"

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Anharmonic Effect of the Unimolecular Dissociation of HFCO and DFCO
(2015-07-01)
Zhong, Jingjun
;
Wang, Weiwen
;
Li, Qian
;
Xia, Wenwen
;
Shao, Ying
The unimolecular reactions of HFCO and DFCO have been studied by RRKM theory. The harmonic and anharmonic rate constants of the HFCO and DFCO decompositions have been calculated. The harmonic and anharmonic rate constants increase with the increasing temperatures and total energies both in the canonical and microcanonical systems. The comparison shows that the rate constants of DFCO decomposition are lower than that of the HFCO decomposition. The anharmonic effect and isotope effect have also been investigated. It has been found that the anharmonic effect and isotope effect are not significant either in the canonical or microcanonical system for all the reactions.
Calculation of anharmonic effects in the unimolecular dissociation of M2+ (H2O)(2) (M = Be, Mg, and Ca)
(2015-11-17)
Li, Qian
;
Yao, Li
;
Xia, Wenwen
;
Lin, S. H.
;
應用化學系
The anharmonic and harmonic rate constants of the unimolecular dissociation of M2+(H2O)(2) (M = Be, Mg, and Ca) were calculated using the Rice-Ramsperger-Kassel-Marcus theory. The anharmonic effects of the reactions were investigated. The results show that the energy barrier of the dissociation of Be2+(H2O)(2) is 68.47 kcal/mol, and the anharmonic (T-4000K = 4.28x10(8) s(-1)) and harmonic (T-4000K = 4.22x10(8) s(-1)) rate constants were close in value in both the canonical and microcanonical systems. The energy barriers of the two steps for the dissociation, Mg2+(H2O)(2) MgOH++H3O+, were 37.41 and 11.39 kcal/mol, and those for the dissociation, Ca2+(H2O)(2) CaOH++H3O+, were 21.15 and 26.42 kcal/mol. The anharmonic effect of the two reactions is significant and cannot be neglected in both the canonical and microcanonical systems. The comparison also shows that the rate constants of the dissociation of Ca2+(H2O)(2) have the maximum values, while those of Be2+(H2O)(2) have the minimum values in the three reactions; however, the anharmonic effect also shows the similar trend in the comparison.
Study on Anharmonic Effect of the Unimolecular Reaction of CH2(D-2)FO
(2014-12-20)
Zhong, Jingjun
;
Li, Qian
;
Luo, Ji
;
Xia, Wenwen
;
Yao, Li
Study on the unimolecular reaction for CH2FO and CD2FO is carried out. The structures, energy barriers and zero point energy of the three channels in the title unimolecular reactions are computed with the MP2/6-311++G(3df, 3pd) method. RRKM theory is used to calculate the rate constants of canonical case at temperature range of 500-5000 K and microcanonical system at total energy of 19.05-71.68 kcal/mol. The results indicate that the anharmonic effect and isotope effect are very small for the three channels, and the anharmonic rate constants, around 10(9)-10(11) s(-1), are close to the experimental prediction reasonably.