Transferability and interpretability of vibrational normalizing-flow coordinates

TL;DR

This paper investigates normalizing-flow vibrational coordinates, which are learned, molecule-specific transformations that improve vibrational calculations by enhancing interpretability and basis-set convergence, and can be generalized across related molecules.

Contribution

It introduces the use of normalizing-flow coordinates for vibrational analysis, demonstrating their utility, interpretability, and transferability across isotopologues and related molecules.

Findings

Normalizing-flow coordinates improve basis-set convergence.

They enhance interpretability of vibrational motions.

Coordinates can be transferred with minimal fine-tuning.

Abstract

The choice of vibrational coordinates is crucial for the accuracy, efficiency, and interpretability of molecular vibrational dynamics and spectra calculations. We explore the recently proposed normalizing-flow vibrational coordinates, which are learned molecule-specific coordinate transformations optimized for a given basis set. Much like how spherical coordinates naturally simplify the hydrogen atom by embedding physical insight into the coordinate system, normalizing-flow coordinates offload complexity from the basis functions into the coordinate transformation itself. This shift not only improves basis-set convergence, but also enhances interpretability of vibrational motions. We provide an analysis of the utility, interpretation and associated constraints of normalizing-flow vibrational coordinates. Moreover, we demonstrate that these coordinates can be generalized across different isotopologues, and even structurally related molecules, achieved with minimal fine-tuning of selected output parameters.