Representation of Reaction Progress

Determine how chemical reaction progress should be represented in a descriptor space suitable for constructing transferable collective variables for enhanced sampling in molecular simulations, addressing the limitations of geometric and system-specific learned descriptors.

Background

The paper argues that most existing reaction collective variables (CVs) are defined in geometric space or learned in a system-specific manner, which limits transferability. While machine-learning approaches optimize CVs, they do not directly resolve the fundamental issue of the physical representation in which reaction progress should be expressed.

From a physical perspective, chemical reactions are defined by electron redistribution. The authors propose using atomic-charge-based electronic CVs as a common charge-space representation, but they frame the broader question of the appropriate representation of reaction progress as a fundamental open issue motivating their work.