The chemisorption thermodynamics of O2 and H2O on AFM UO2 surfaces unraveled by DFT+U-D3 study
Abstract
Unraveling the adsorption mechanism and thermodynamics of O2 and H2O 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 UO2 surfaces and propose the 1k AFM surface computational model. The chemisorption states of O2 and H2O on UO2 (111) surface, suggested by previous experiments, are accurately calculated for the first time. The adsorption properties of O2 and H2O on UO2(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 O2 and H2O on UO2 surfaces. Due to the different intermolecular interactions, the monolayer and multilayer adsorption models are identified for O2 and H2O, respectively. This study has comprehensively revealed the different adsorption mechanisms of O2 and H2O on UO2 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.
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