The chemisorption thermodynamics of O$_2$ and H$_2$O on AFM UO$_2$ surfaces unraveled by DFT+U-D3 study

TL;DR

This study uses advanced DFT+U-D3 calculations to analyze how O$_2$ and H$_2$O chemisorb on UO$_2$ surfaces, revealing distinct adsorption mechanisms and thermodynamic behaviors relevant to nuclear fuel corrosion.

Contribution

It introduces a new computational model for UO$_2$ surfaces and systematically characterizes the chemisorption phase diagram of O$_2$ and H$_2$O, bridging electronic structure and experimental insights.

Findings

Different adsorption mechanisms for O$_2$ and H$_2$O on UO$_2$ surfaces.

Identification of monolayer and multilayer adsorption models.

Systematic thermodynamic phase diagrams for chemisorption states.

Abstract

Unraveling the adsorption mechanism and thermodynamics of O$_2$ and H$_2$O on uranium dioxide surfaces is critical for the nuclear fuel storage and uranium corrosion. Based on the first-principles DFT+U-D3 calculations, we carefully test the effect of antiferromagnetic order arrangements on the thermodynamic stability of UO$_2$ surfaces and propose the 1k AFM surface computational model. The chemisorption states of O$_2$ and H$_2$O on UO$_2$ (111) surface, suggested by previous experiments, are accurately calculated for the first time. The adsorption properties of O$_2$ and H$_2$O on UO$_2$(111) and (110) surfaces are discussed in detail to reveal the different interaction mechanisms. Combined with ab initio atomistic thermodynamics method, we systematically calculate the chemisorption phase diagram and isotherm of O$_2$ and H$_2$O on UO$_2$ surfaces. Due to the different intermolecular interactions, the monolayer and multilayer adsorption models are identified for O$_2$ and H$_2$O, respectively. This study has comprehensively revealed the different adsorption mechanisms of O$_2$ and H$_2$O on UO$_2$ surfaces, bridging the electronic structure calculations to the interpretation of experimental results and providing a solid foundation for future theoretical studies of uranium corrosion mechanism in humid air.