Stepwise kinetics of the early-stage nucleation in chiral perovskites via ab initio molecular dynamics and free-energy calculations

Abstract

This study provides a comprehensive molecular-level understanding of the early-stage nucleation process in chiral hybrid organic–inorganic perovskites (HOIPs). A combination of ab initio molecular dynamics (AIMD) based on density functional theory (DFT) and parallel bias metadynamics simulations was designed to explore a broad spectrum of the nucleation scenarios, disclosing how structural deviations affect the formation of chiral aggregates at the atomic scale. The workflow uses parallel replicas initialized from configurations characterised by different root-mean-square deviations (RMSD) relative to the crystallographic coordinates of the chiral ligands. The free-energy landscape and the kinetic pathways involved in chiral aggregate formation indicate a stepwise mechanism that governs the transition from disordered to chiral states. The computed free-energy barriers and corresponding transition timescales uncover several critical stages in this process, including rapid initial relaxations as well as slower, free-energy-intensive steps, with overall timescales on the order of microseconds as the system approaches its most chiral configuration.