Mechanochemistry on the Müller–Brown surface by Newton trajectories

Abstract

Chemical processes which suffer the application of mechanical force are theoretically described by effective potential energy surfaces (PES). We worked out [Theor. Chem. Acc. 135, 113 (2016)] that the changes due to the force for the minimums and for the saddle points can be described by Newton trajectories (NT) of the original PES. If the force is so high that the saddle point disappears into a shoulder then the mechanochemical action is fulfilled: the pulling force breaks down the reaction barrier. The point is named barrier breakdown point (BBP). Different families of NTs form corridors on the original PES which describe qualitative different actions of the force. The border regions of such corridors are governed by the valley-ridge inflection points (VRI) of the surface. Here we discuss all this on the basis of the well known Müller-Brown (MB) surface, and we describe a new kind of NT-corridor.

Toward a theory of mechanochemistry: Simple models from the very beginnings

“…Our main point, and interest, is the understanding of the direction of a given external force, which decides which reaction valley on the PES is used for an induced reaction. To establish the relevance of our former works we go back here to the early beginnings of the pulling of very small molecular models. The model ansatz of Equations and allows to theoretically treat the influence of an external force, f , on the PES of a molecule.…”

“…Note that coupled degrees of freedom of the PES, but under a fixed force direction, are treated elsewhere. [49,53,54,63,66]…”

“…Our main point, and interest, is the understanding of the direction of a given external force, which decides which reaction valley on the PES is used for an induced reaction. To establish the relevance of our former works [49,53,54,63,64,66,76] we go back here to the early beginnings of the pulling of very small molecular models. The model ansatz of Equations (1) and (2) Sometimes one assumes, to explain molecular pulling experiments, that the force, f, acts directly along a "reaction coordinate" to reach the new, effective transition state of an induced reaction.…”

“…The symbolic point between f and x means the scalar product. This is explained elsewhere . The dimension of the vectors, f and x , is N = 3 n − 6 internal coordinates, and n is the number of atoms of the treated molecule.…”

“…This is explained elsewhere. [49] The dimension of the vectors, f and x, is N = 3n − 6 internal coordinates, and n is the number of atoms of the treated molecule. The vector of the force, f, is determined by two properties: its direction and its length.…”