Hydrogen Bonds in Lead Halide Perovskites: Insights from <i>Ab Initio</i> Molecular Dynamics

Hydrogen bonds (HBs) play an important role in the rotational dynamics of organic cations hybrid organic/inorganic halide perovskites, thus affecting structural and electronic properties perovskites. However, even existence HBs these perovskites are not well established. In this study, we investigate MAPbBr3 (MA+ = CH3NH3+), FAPbI3 (FA+ CH(NH2)2+), their solid solution with composition (FAPbI3)7/8(MAPbBr3)1/8, using ab initio molecular structure calculations. We consider donated by X-H fragments (X N C) accepted halides (Y Br I) characterize based on pair distribution functions a combined function hydrogen–acceptor distance donor–hydrogen–acceptor angle. By analyzing functions, establish geometrical criteria for HB (H–Y) angle (X–H–Y). The condition is defined as d(H – Y) < 3 Å N–H-donated 4 C–H-donated HBs. angular 135° H 180° both types A considered to be formed when conditions simultaneously satisfied. At simulated temperature (350 K), dynamically break form. compute time correlation lifetimes, which range between 0.1 0.3 ps at that temperature. analysis lifetimes indicates N–H–Br relatively stronger than N–H–I bonds, while C–H–Y weaker, minimal influence from cation. To evaluate impact vibrational spectra, present power spectrum region N–H C–H stretching modes, comparing them normal mode frequencies isolated cations. show peaks associated modes redshifted asymmetrically deformed, do exhibit effects.