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This research aims to elucidate the atomic-level dynamics of HfB2 oxidation mechanisms in extreme environments.

June 5, 2026Inorganic Chemistry0 citations

Atomic-Level Insights into the HfB 2 Oxidation Mechanism by the Combination of Density Functional Theory and Ab Initio Molecular Dynamics Calculations

YXYidan Xing RZRuxian Zhang JCJiagang Chen

Key Points

This research aims to elucidate the atomic-level dynamics of HfB2 oxidation mechanisms in extreme environments.
Combined density functional theory (DFT) calculations and ab initio molecular dynamics (AIMD) simulations were employed.
Oxidation processes were examined at temperatures of 973 K and 1673 K.
Investigation of reaction pathways and energy barriers for O2 dissociation on Hf- and B-terminated surfaces.
Spontaneous O2 dissociation occurs on the Hf-terminated surface, forming a protective HfO2 layer.
An energy barrier of 0.28 eV is required for O2 dissociation on the B-terminated surface, leading to structural degradation.
Higher temperatures accelerate oxygen diffusion, enhancing the overall oxidation rate.

Abstract

High-temperature oxidation of HfB2 governs its long-term stability in extreme environments, yet the atomistic dynamics of surface oxidation remain incompletely elucidated. Herein, the oxidation process of the HfB2(0001) surface was systematically investigated by combining density functional theory (DFT) calculations and ab initio molecular dynamics (AIMD) simulations. The results show that O2 undergoes spontaneous dissociation on the Hf-terminated surface, forming a HfO2 layer that effectively suppresses further oxygen adsorption. In contrast, O2 dissociation on the B-terminated surface requires overcoming an energy barrier of 0.28 eV, and the resulting BO3 units lead to surface structural degradation. AIMD simulations at 973 and 1673 K further demonstrate distinct reaction pathways: on the Hf-terminated surface, O atoms react exclusively with the surface Hf atoms; on the B-terminated surface, O atoms initially form B2O3 units, subsequently diffuse into the subsurface layer, and react with Hf atoms beneath the surface. This process involves reaction intermediates evolving sequentially from HfB2O to Hf2B2O, then to Hf3BO, and finally transforming into Hf3O. Notably, an elevated temperature accelerates oxygen diffusion and intermediate transformation, increasing the oxidation rate. These findings provide atomic-scale theoretical insights into HfB2 oxidation and establish a basis for optimizing the oxidation resistance.

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