Construction of Potential Energy Surfaces for Reactions With Post‐Transition State Bifurcations Using Principal Component Analysis

Constructing low-dimensional potential energy surfaces (PESs) for complex reactions remains challenging, particularly for systems exhibiting post-transition state bifurcations (PTSBs) where traditional measures of reaction coordinates are often inadequate. We introduce a principal component analysis (PCA)-assisted method for constructing two-dimensional PESs that avoids reliance on predefined coordinates or intrinsic reaction paths. In this method, PCA is applied to collections of key geometries to identify dominant structural variations from multiple internal coordinates. The resulting principal components are then used to drive relaxed surface scans. Projection of ab initio molecular dynamics (AIMD) trajectories onto these PESs helps users connect PES shape and dynamical behavior.