# Evolution of High-Temperature Oxygen Clusters and Radical Release: A Molecular Dynamics Study in Pure Oxygen and Titanium Tetrachloride Oxidation Environments

## TL;DR

The study reveals how oxygen clusters at high temperatures release radicals, influencing oxide material synthesis, alloy corrosion, and combustion.

## Contribution

A novel 'oxygen clustering–radical release' pathway is identified as a universal source of radicals in high-temperature oxidation.

## Key findings

- Odd-numbered oxygen clusters (like O3) are reactive and release radicals upon reaching a critical size.
- Even-numbered clusters (like O6/O8) are inert and do not release radicals.
- The radical release mechanism is consistent in both pure O2 and TiCl4-containing environments.

## Abstract

What are the main findings?
The “oxygen clustering–radical release” pathway is identified in high-temperature oxidation.Odd-numbered oxygen clusters (dominated by O3) are reactive while even-numbered are inert.Reaching a critical size, the cluster releases radicals that persist in pure O2 and TiCl4-containing environments.

The “oxygen clustering–radical release” pathway is identified in high-temperature oxidation.

Odd-numbered oxygen clusters (dominated by O3) are reactive while even-numbered are inert.

Reaching a critical size, the cluster releases radicals that persist in pure O2 and TiCl4-containing environments.

What are the implications of the main findings?
Provides a novel mechanism for the controlled synthesis of functional oxide materials.Offers a new perspective for understanding the high-temperature oxidation corrosion mechanisms of alloy materials.Holds implications for the high-temperature combustion processes of fuel materials.

Provides a novel mechanism for the controlled synthesis of functional oxide materials.

Offers a new perspective for understanding the high-temperature oxidation corrosion mechanisms of alloy materials.

Holds implications for the high-temperature combustion processes of fuel materials.

Despite decades of research into high-temperature oxidation kinetics, the atomic-scale origin of oxygen radical formation—a critical driver of the synthesis of functional oxide materials, oxidation corrosion of alloys, and combustion of fuels—remains elusive. Here, we unveil a previously unrecognized “oxygen clustering–radical release” pathway at the molecular level, wherein transient van der Waals aggregates of oxygen molecules, rather than isolated O2, serve as the primary radical source. Through an integrated computational strategy combining first-principles calculations and deep neural network potential function molecular dynamics, we demonstrate that oxygen clusters exhibit a pronounced odd–even oscillation in stability: even-numbered clusters (especially O6/O8 subunits) are chemically inert, whereas odd-numbered clusters (dominated by O3) possess high reactivity. Kinetically, clusters evolve via reversible aggregation–dissociation, and upon reaching a critical size, undergo structural collapse accompanied by radical release—a process initiated predominantly by large odd-numbered clusters. This mechanism persists in both pure O2 and TiCl4-containing environments, with TiCl4 modulating only the aggregation kinetics, not the fundamental pathway. Our work establishes oxygen clustering as a universal, spontaneous source of radicals in high-temperature oxidation, providing a new molecular-level mechanistic framework for understanding and controlling radical-driven processes in materials synthesis, corrosion and combustion.