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Hydrogen bonds in lead halide perovskites: insights from ab initio molecular dynamics

Garrote-Marquez, A., Lodeiro, L., Suresh, R., Cruz Hernandez, N., Grau-Crespo, R. ORCID: and Menendez-Proupin, E. (2023) Hydrogen bonds in lead halide perovskites: insights from ab initio molecular dynamics. Journal of Physical Chemistry C, 127 (32). pp. 15901-15910. ISSN 1932-7447

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To link to this item DOI: 10.1021/acs.jpcc.3c02376


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, C) of the organic cations and accepted by the halides (Y=Br, I), and characterize their properties based on pair distribution functions and on a combined distribution function of hydrogen-acceptor distance with donor-hydrogen-acceptor angle. By analyzing these functions, we establish geometrical criteria for HB existence based on 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 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 minimal influence from the halide and cation. To evaluate the impact of HBs on 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.

Item Type:Article
Divisions:Life Sciences > School of Chemistry, Food and Pharmacy > Department of Chemistry
ID Code:112803
Publisher:American Chemical Society


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