Vona Cecilia, Dankl Mathias, Boziki Ariadni, Bircher Martin P, Rothlisberger Ursula
Laboratory of Computational Chemistry and Biochemistry, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
J Phys Chem C Nanomater Interfaces. 2025 Jan 30;129(6):3040-3053. doi: 10.1021/acs.jpcc.4c04979. eCollection 2025 Feb 13.
Lead halide perovskites have emerged as highly efficient solar cell materials. However, to date, the most promising members of this class are polymorphs in which a wide-band-gap δ phase competes with the photoactive perovskite α form and the intrinsic physical interactions that stabilize one phase over the other are currently not well understood. Classical molecular dynamics simulations based on suitably parametrized force fields (FF) enable computational studies over broad temperature (and pressure) ranges and can help to identify the underlying factors that govern relative phase stability at the atomic level. In this article, we present a force-matching-based approach for the automatized generation of polarizable () as well as nonpolarizable () FFs from high-level reference data and apply it to the all-inorganic lead halide material CsPbI as a prototype system exhibiting a δ/α polymorphism. These force-matched and FFs have been determined based on extensive reference data from first-principles molecular dynamics simulations over a wide range of temperatures. While both FFs are able to describe the perovskite as well as the nonperovskite δ phase, finer structural details, as well as the relative phase stability, are better reproduced with the polarizable version. A comparison of these ab initio-derived interatomic potentials allows direct insight into the physical origin of the interactions that govern the interplay between the two competing phases. It turns out that explicit polarization is the essential factor that stabilizes the strongly anisotropic δ phase over the high-symmetry (cubic) perovskite α phase at lower temperatures. This fundamental difference between α and δ phases appears universal and might thus also hold for other perovskite compounds with δ/α polymorphism providing rational guidance for synthetic efforts to stabilize the photoactive perovskite phase at room temperature.
卤化铅钙钛矿已成为高效太阳能电池材料。然而，迄今为止，这类材料中最有前景的成员是多晶型物，其中宽带隙δ相与光活性钙钛矿α相竞争，而目前尚不清楚稳定一个相优于另一个相的内在物理相互作用。基于适当参数化力场（FF）的经典分子动力学模拟能够在较宽的温度（和压力）范围内进行计算研究，并有助于确定在原子水平上控制相对相稳定性的潜在因素。在本文中，我们提出了一种基于力匹配的方法，用于从高级参考数据自动生成可极化（）以及不可极化（）的力场，并将其应用于全无机卤化铅材料CsPbI，作为具有δ/α多晶型的原型系统。这些力匹配的和力场是基于在广泛温度范围内的第一性原理分子动力学模拟的大量参考数据确定的。虽然这两种力场都能够描述钙钛矿相以及非钙钛矿δ相，但可极化版本能更好地再现更精细的结构细节以及相对相稳定性。对这些从头算得到的原子间势的比较，能够直接洞察控制两个竞争相之间相互作用的物理起源。结果表明，明确的极化是在较低温度下稳定强各向异性的δ相优于高对称（立方）钙钛矿α相的关键因素。α相和δ相之间的这种根本差异似乎具有普遍性，因此对于其他具有δ/α多晶型的钙钛矿化合物可能也成立，为在室温下稳定光活性钙钛矿相的合成努力提供合理指导。
