A new (cartesian) reaction-path model for dynamics in polyatomic systems, with application to H-atom transfer in malonaldehyde

Abstract

A new kind of reaction-path model for describing reactions in polyatomic molecular systems is presented, based on the cartesian coordinates of the atoms. Not only does this lead to a simpler treatment of the interaction between the ‘system’(i.e. the reaction coordinate) and the ‘bath’(the other degrees of freedom) than earlier reaction-path, models based on the (curvilinear) steepest-descent reaction path, but in many cases it also provides a more natural description of the dynamics. The resulting Hamiltonian has the standard form of a cartesian ‘system’ linearly coupled to a harmonic ‘bath’, the dynamics of which is treated in this paper by the basis set method of Makri and Miller (J. Chem. Phys., 1987, 86, 1451). Application to a model of H-atom transfer in malonaldehyde shows that the overall approach (both the cartesian reaction-path model and the basis-set method treatment of the dynamics) is quite successful.