Critical Evaluation of Five Classical Force Fields for CsPbI₃: Limitations in Modeling Phase Stability and Transformations

Abstract

The poor stability of perovskite materials can be comprehensively understood at the atomic level through molecular simulations based on classical force fields. The accuracy of these force fields significantly impacts the reliability and precision of information obtained from molecular simulations. This study presents a detailed evaluation of five CsPbI3 force fields developed after 2020, namely, LJ-Coul, B-Coul, EABC, AMOEBA, and ReaxFF, with a specific focus on their ability to accurately describe the stability and phase transitions of CsPbI3 polymorphs. Among the five force fields evaluated, only LJ-Coul demonstrates reasonably accurate descriptions of the thermodynamic stability and phase transitions of the CsPbI3 system, while the other four force fields encounter various issues. Specifically, the B-Coul force field fails to stabilize δ-CsPbI3 at 300 K and other structures at high temperatures. The EABC force field inaccurately predicts the CsPbI3 perovskite phases. The AMOEBA and ReaxFF force fields underestimate the stabilities of δ- and α-CsPbI3, respectively. A thorough analysis of these issues is provided along with proposed improvement methods. The insights gained from this study are invaluable for selecting an appropriate force field for CsPbI3 and offer significant guidance for future force field development pertaining to related materials.