Thermally Activated Fluxionality Accelerates Nonradiative Decay in Titania Nanoclusters

Area of Science:

• Materials Science
• Physical Chemistry
• Computational Chemistry

Background:

• Photoactive nanoclusters are typically modeled as static, single-structure entities.
• Thermal energy allows for multiple accessible configurations beyond the lowest energy state.

Purpose of the Study:

• To investigate the role of thermal fluxionality in the excited-state dynamics of oxide nanoclusters.
• To understand how structural rearrangements influence energy relaxation and charge recombination.

Main Methods:

• Utilized ab initio molecular dynamics (AIMD) for simulating atomic motion.
• Employed time-dependent density functional theory (TD-DFT) for electronic structure calculations.
• Performed nonadiabatic dynamics simulations to track excited-state processes.

Main Results:

• Identified a fluxional mode enabling low-energy structural rearrangement in a model titania nanocluster.
• Observed that this fluxionality broadens the S1 excitation-energy distribution, creating a bimodal profile.
• Found accelerated S1 relaxation due to altered decay pathways and enhanced ground-state recombination via coupled S0-S1 configurations.

Conclusions:

• Local coordination fluxionality is a key mechanism for reshaping excited-state landscapes in oxide nanoclusters.
• This phenomenon offers a route to tune nonradiative decay and charge recombination in photocatalysis.
• Findings have implications for designing advanced photocatalytic metal oxides.