The Finite Temperature Structure of the MAPbI3 Perovskite: Comparing Density Functional Approximations and Force Fields to Experiment

Abstract

Determining the finite temperature structure of the hybrid perovskite MAPbI3 is a challenge for both experimental and theoretical methods. A very powerful computational method that can resolve the atomic structure is molecular dynamics (MD). The resulting structure depends on the density functional approximation (DFA) in the case of ab initio MD and the force field in classical MD. We compare the structure between 250K and 400K obtained with different DFAs and force fields in one consistent manner. The symmetry of the PbI3 framework is analyzed as well as the relative ordering of the neighboring organic molecules inside the framework. The distribution function of the molecules is used to map out an effective energy surface for the rotation of a single molecule. This surface is accurately modeled by a pair of cubic harmonics. Available experimental data in literature are discussed and compared to the structure obtained with the different methods. The spread in these data is still too large to uniquely determine the method that 'best' describes the perovskite, however promising candidates and outliers have been identified.

arXiv comment15 pages, 8 figures

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• Structure and Binding in Halide Perovskites: Analysis of Static and Dynamic Effects from Dispersion-Corrected Density Functional Theory
• Exploring librational pathways with on-the-fly machine-learning force fields: Methylammonium molecules in MAPbX${}_3$ (X=I, Br, Cl) perovskites
• Long-range order imposed by short-range interactions in methylammonium lead iodide: Comparing point-dipole models to machine-learning force fields
• Domain boundaries in Luttinger-Tisza ordered dipole lattices