Exploring the Origin of Molecular Chirality: A Standalone Suite of Tools to Visualize and Analyze Transition Current Density.

In this paper, we present a new software suite dedicated to the study and analysis of chiroptical signals and their nature. Beyond the simple evaluation of dipolar moments associated with either electronic or vibrational transitions, the tools it provides are able to compute and represent transition current densities (TCDs), which are directly connected to the electronic contribution to dipole transition moments. By mapping the corresponding vector fields into the real space, details on the sign and magnitude of the rotational strengths can be revealed in terms of localized current patterns on atoms, bonds, and functional groups, offering a unique view into the origins of chiroptical signatures. The software, open-source, is composed of two units: one to generate the fields from standard electronic structure calculations, and a visualization library that supports different representations to highlight, in the most suitable way, the influence of local regions in the systems under study on the overall chiral response. The capabilities of these tools are illustrated through a variety of cases, considering organic and organometallic molecules, closed- and open-shell species, under electronic and vibrational transitions. By making TCD analysis routine for a large range of molecular systems, this suite bridges the gap between black-box simulations of electronic and vibrational circular dichroism and chemically intuitive interpretations of molecular chirality.