An atomistic modelling approach to the thermodynamic and structural response of zirconium to hydrogen-defect interactions

Abstract

Zirconium and its alloys are widely used in nuclear applications due to their low neutron absorption, corrosion resistance, and favorable mechanical properties. However, hydrogen uptake and irradiation-induced defects (vacancies and self-interstitial atoms (SIAs)) can significantly degrade performance. In this work, molecular dynamics simulations are employed to investigate the coupled effects of hydrogen and point defects on the thermodynamic, elastic, and thermal transport properties of zirconium within the low-concentration regime (0–2%). Interactive configurations, where hydrogen and defects coexist, are systematically compared with non-interactive systems containing only hydrogen or only defects. Results show that hydrogen alone increases lattice stiffness, reflected by rising average sound velocity and Debye temperature, while reducing anharmonicity. Conversely, vacancies and SIAs induce lattice softening, lower sound velocities, and increase anharmonicity. When hydrogen and defects coexist, their interactions significantly modify these trends: vacancies and SIAs suppress hydrogen-induced stiffening, while hydrogen partially mitigates defect-driven degradation. Thermal transport analysis reveals only minor variations in minimum thermal conductivity across all systems. Density evolution demonstrates a mutual compensation effect between hydrogen-induced expansion and defect-induced mass depletion. Overall, these findings highlight a complex but stabilizing interplay between hydrogen and point defects, providing valuable insight for predicting zirconium behavior under nuclear reactor conditions.