Formation and Recombination Dynamics of Polarons in Goethite: A Time-Domain Ab Initio Study

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Chemistry

Background:

• Polaron dynamics are critical for charge transport in materials.
• Temperature and local atomic structure (coordination environment) are known to influence these dynamics.
• Understanding these effects is key to designing advanced functional materials.

Purpose of the Study:

• To investigate the influence of temperature and coordination environment on polaron formation and recombination.
• To model polaron behavior in goethite (FeOOH) under various conditions.
• To compare polaron dynamics in FeOOH with those in related iron oxides like Fe2O3.

Main Methods:

• Utilized ab initio calculations to study electronic and structural properties.
• Employed nonadiabatic molecular dynamics (NAMD) simulations to capture dynamic polaron behavior.
• Simulated conditions included electron injection, photoexcitation, and heterovalent doping.

Main Results:

• Polaron formation in FeOOH is temperature-dependent, proceeding via an adiabatic mechanism with faster formation at higher temperatures.
• Only electron polarons were observed in FeOOH, irrespective of the formation method.
• Photoexcited electron polaron recombination is significantly faster in FeOOH compared to Fe2O3 due to its distinct coordination environment, leading to enhanced charge-phonon scattering and nonadiabatic coupling.

Conclusions:

• Temperature and coordination environment are critical factors governing polaron dynamics.
• The unique coordination in FeOOH facilitates faster polaron recombination.
• Findings provide essential insights for the rational design of materials with optimized charge carrier dynamics.