The Dynamical Significance of Valley-Ridge Inflection Points

TL;DR

This study shows that valley-ridge inflection points on a potential energy surface significantly influence the dynamics of chemical reactions, affecting trajectory recrossings and reaction pathways.

Contribution

The paper introduces a symmetric potential energy function allowing control over VRI point location while fixing critical points, enabling a detailed dynamical analysis.

Findings

VRI point location influences trajectory recrossings.

Trajectory behavior depends on energy and VRI position.

VRI controls the fraction of trajectories avoiding potential wells.

Abstract

In this paper we demonstrate that valley-ridge inflection (VRI) points of a potential energy surface (PES) have a dynamical influence on the fate of trajectories of the underlying Hamiltonian system. These points have attracted the attention of chemists in the past decades when studying selectivity problems in organic chemical reactions whose energy landscape exhibits a post-transition-state bifurcation in the region between two sequential saddles without an intervening energy minimum. To address the dynamical significance of valley-ridge inflection points, we construct a symmetric potential energy function that allows us to move the location of the VRI point while keeping the locations and energies of the critical points fixed. In this setup, we carry out a parametric study of the dynamical behavior of ensembles of trajectories in terms of the energy of the chemical system and the position of the VRI point. Our analysis reveals that the location of the VRI point controls the fraction of trajectories that recross the high energy saddle region of the PES without entering either of the potential wells that are separated by the low energy saddle.