Picosecond lifetimes of hydrogen bonds in the halide perovskite CH$_3$NH$_3$PbBr$_3$

TL;DR

This study investigates the ultrafast dynamics of hydrogen bonds in the perovskite CH$_3$NH$_3$PbBr$_3$ using molecular simulations, revealing their rapid lifetimes and impact on vibrational properties across a wide temperature range.

Contribution

It provides the first detailed analysis of hydrogen bond lifetimes and their temperature dependence in this perovskite using machine-learning force fields.

Findings

Hydrogen bond lifetimes decrease from 7.6 ps to 0.16 ps with temperature.

Hydrogen bonds influence vibrational spectra and physical properties.

Geometric hydrogen bond criteria remain consistent across temperatures.

Abstract

The structures and properties of organic-inorganic perovskites are influenced by the hydrogen bonding between the organic cations and the inorganic octahedral networks. This study explores the dynamics of hydrogen bonds in CH$_3$NH$_3$PbBr$_3$ across a temperature range from 70 K to 350 K, using molecular dynamics simulations with machine-learning force fields. The results indicate that the lifetime of hydrogen bonds decreases with increasing temperature from 7.6 ps (70 K) to 0.16 ps (350 K), exhibiting Arrhenius-type behaviour. The geometric conditions for hydrogen bonding, which include bond lengths and angles, maintain consistency across the full temperature range. The relevance of hydrogen bonds for the vibrational states of the material is also evidenced through a detailed analysis of the vibrational power spectra, demonstrating their significant effect on the physical properties for this class of perovskites.