| In this paper,based on the basic principles of quantum mechanics and statistical physics,the microscopic mechanisms of the transformation of molecular complexes between the simplest Criegee intermediate and ketones have been studied by using the electronic structure methods,canonical transition state theory method,and canonical variational transition state theory with multidimensional small curvature quantum tunneling.The simplest Criegee intermediate with acetone and methyl vinyl ketone molecules has been explored to form intermolecular complexes and further transformation.Details are listed as follows:The theoretical results show that reliable geometrical structure,zero point vibration energy,and single point energy are needed to quantitatively describe the microscopic mechanism of the transformation of molecular complexes between the simplest Criegee intermediate and acetone and methyl vinyl ketone.The results show that DF-CCSD(T)-F12 b can obtain reliable geometric structure and zero point vibration energy of key stationary points at jun-cc-p VDZ level.However,for single point energy calculations,it is necessary to include the coupled cluster theory method to perturbate the fourth order excitation,that is,the compound energy method W3X-L can obtain the quantitative barrier height.In order to obtain the potential energy surface of the transition between the simplest Criegee intermediate and the complexes of acetone and methyl vinyl ketone,the calculated results verify that the density functional theory M11-L with MG3 S can reliably describe the potential energy surface of the transition between the simplest Criegee intermediate and the complexes of acetone and methyl vinyl ketone.In order to quantitatively describe the rate of the transformation of molecular complexes between the simplest Criegee intermediate and acetone and methyl vinyl ketone,the reaction kinetics was calculated using a dual-level calculation strategy based on the basic principles of statistical physics.The thermodynamic parameter information of canonical transition state theory method at the high level is combined with canonical variational transition state theory at the low level of density functional theory and the direct dynamic calculation of multidimensional small curvature quantum tunneling.The kinetic parameters of the reaction are obtained in the range of experimental accuracy.The results reveal that the microscopic mechanism of the transformation of molecular complexes between the simple Criegee intermediate and acetone and methyl vinyl ketone is a stepwise mechanism,which revises the previous research results in one step.And this stepwise reaction mechanism is also the microscopic mechanism for the transformation of other Criegee intermediates into aldehydes.These theoretical dynamics validate the reliability of the experimental results and supplement the theoretical data.It has contributed to atmospheric simulation. |
