Hydrogen Bonds in Lead Halide Perovskites: Insights from Ab Initio Molecular Dynamics

Alejandro Garrote-Márquez; Lucas Lodeiro; Rahul Suresh; Norge Cruz Hernández; Ricardo Grau-Crespo; Eduardo Menéndez-Proupin

doi:10.1021/acs.jpcc.3c02376

Hydrogen Bonds in Lead Halide Perovskites: Insights from Ab Initio Molecular Dynamics

J Phys Chem C Nanomater Interfaces. 2023 Aug 8;127(32):15901-15910. doi: 10.1021/acs.jpcc.3c02376. eCollection 2023 Aug 17.

Authors

Alejandro Garrote-Márquez¹, Lucas Lodeiro², Rahul Suresh^{1

3}, Norge Cruz Hernández¹, Ricardo Grau-Crespo⁴, Eduardo Menéndez-Proupin¹

Affiliations

¹ Departamento de Física Aplicada I, Escuela Politécnica Superior, Universidad de Sevilla, Seville E-41011, Spain.
² Departamento de Química, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, Santiago, Ñuñoa 7800003, Chile.
³ International Research Center of Spectroscopy and Quantum Chemistry - IRC SQC, Siberian Federal University, 79 Svobodny pr., 660041 Krasnoyarsk, Russia.
⁴ Department of Chemistry, Whiteknights, University of Reading, Reading RG6 6DX, UK.

Abstract

Hydrogen bonds (HBs) play an important role in the rotational dynamics of organic cations in hybrid organic/inorganic halide perovskites, thus affecting the structural and electronic properties of the perovskites. However, the properties and even the existence of HBs in these perovskites are not well established. In this study, we investigate HBs in perovskites MAPbBr₃ (MA⁺ = CH₃NH₃⁺), FAPbI₃ (FA⁺ = CH(NH₂)₂⁺), and their solid solution with composition (FAPbI₃)_7/8(MAPbBr₃)_1/8, using ab initio molecular dynamics and electronic structure calculations. We consider HBs donated by X-H fragments (X = N and C) of the organic cations and accepted by the halides (Y = Br and I) and characterize their properties based on pair distribution functions and on a combined distribution function of the hydrogen-acceptor distance with the donor-hydrogen-acceptor angle. By analyzing these functions, we establish geometrical criteria for HB existence based on the hydrogen-acceptor (H-Y) distance and donor-hydrogen-acceptor angle (X-H-Y). The distance condition is defined as d(H - Y) < 3 Å for N-H-donated HBs and d(H - Y) < 4 Å for C-H-donated HBs. The angular condition is 135^° < (X - H - Y) < 180^° for both types of HBs. A HB is considered to be formed when both angular and distance conditions are simultaneously satisfied. At the simulated temperature (350 K), the HBs dynamically break and form. We compute the time correlation functions of HB existence and HB lifetimes, which range between 0.1 and 0.3 ps at that temperature. The analysis of HB lifetimes indicates that N-H-Br bonds are relatively stronger than N-H-I bonds, while C-H-Y bonds are weaker, with a minimal influence from the halide and cation. To evaluate the impact of HBs on the vibrational spectra, we present the power spectrum in the region of N-H and C-H stretching modes, comparing them with the normal mode frequencies of isolated cations. We show that the peaks associated with N-H stretching modes in perovskites are redshifted and asymmetrically deformed, while the C-H peaks do not exhibit these effects.