Towards a Theory of Mechanochemistry, Simple Models from the Very Beginnings

by

Wolfgang Quapp,  Josep Maria Bofill  and  Jordi Ribas-Arino

submitted to Int J Quant Chem  2018 


A core idea in the context of mechanochemistry is that applying an external
tensile force along a reaction coordinate should enhance the chemical reaction of
interest. Here we analyze perturbed generic molecular structures:
schematic models of triatomics, ABC, and tetraatomics, AABB. They are used
to demonstrate that pulling does usually not use the 'reaction coordinate', 
but opens new reaction pathways. Within development of these models we use the 
concept of Newton trajectories for a theory of mechanochemistry.
However, we find cases where the theory of Newton trajectories is not
applicable.  For all cases we define the curve of force-displaced stationary points, 
and we discuss the importance of barrier breakdown points and valley-ridge 
inflection points.  The examples use Morse potentials for bonds and simple 
angle functions and are demonstrated by assumed real values for the 
potential parameters. On the basis of the systematic study of some generic 
models we explain a set of already observed experimental mechanochemical
phenomena in specific molecular systems and we apply the results to the 
strength of chemical bonds.

Keywords: Mechanochemistry, Force displaced stationary points, Barrier
          breakdown point, Valley-Ridge inflect point, Newton trajectory, 
          Force-extension curve