Kaiser Waldemar, Carignano Marcelo, Alothman Asma A, Mosconi Edoardo, Kachmar Ali, Goddard William A, De Angelis Filippo
Computational Laboratory for Hybrid/Organic Photovoltaics (CLHYO), Istituto CNR di Scienze e Tecnologie Chimiche "Giulio Natta" (CNR-SCITEC), Via Elce di Sotto 8, 06123 Perugia, Italy.
Department of Biomedical Engineering, Northwestern University, Evanston, Illinois 60208, United States.
J Phys Chem Lett. 2021 Dec 16;12(49):11886-11893. doi: 10.1021/acs.jpclett.1c03428. Epub 2021 Dec 7.
First-principles molecular dynamics (FPMD) represents a valuable tool to probe dynamical properties of metal-halide perovskites (MHPs) which are key to their success in optoelectronic devices. Most FPMD studies rely on generalized gradient approximation (GGA) functionals for computational efficiency matters, while hybrid functionals, although computationally demanding, are usually needed to accurately describe structural and electronic properties of MHPs. This Letter reports FPMD simulations on CsPbI based on the hybrid PBE0 functional. Our results demonstrate that PBE0 leads to lattice parameters and phonon modes in excellent agreement with experimental data, while GGA results overestimate the lattice parameter and the electronic band gap and underestimate the phonon energies. Our FPMD results also shed light on anharmonic effects and double-well instabilities in the octahedral tilting, highlighting a lowered free energy barrier for PBE0 and farther separated potential wells. Our results suggest that hybrid functionals are required to accurately describe crystal structure, lattice dynamics, and anharmonicity in MHPs.
第一性原理分子动力学（FPMD）是探究金属卤化物钙钛矿（MHP）动力学性质的一种重要工具，而这些性质是其在光电器件中取得成功的关键。大多数FPMD研究出于计算效率的考虑依赖于广义梯度近似（GGA）泛函，然而，尽管混合泛函计算量很大，但通常需要用它们来准确描述MHP的结构和电子性质。本文报道了基于混合PBE0泛函对CsPbI进行的FPMD模拟。我们的结果表明，PBE0得出的晶格参数和声子模式与实验数据高度吻合，而GGA的结果高估了晶格参数和电子带隙，低估了声子能量。我们的FPMD结果还揭示了八面体倾斜中的非谐效应和双阱不稳定性，突出了PBE0较低的自由能垒和更远的分离势阱。我们的结果表明，需要混合泛函来准确描述MHP中的晶体结构、晶格动力学和非谐性。
