Thermodynamic and structural evolution of lithium–oxygen–deuterium systems across fusion-relevant temperature and composition ranges

We have investigated the thermodynamic, structural, and transport properties of lithium–oxygen (Li–O) and lithium–oxygen–deuterium (Li–O–D) systems using molecular dynamics over a temperature range of 100–1500 K. Rapid quenching yields glassy and amorphous phases, enabling comparisons with liquid and crystalline states. Deuterium addition suppresses crystallization and enhances hydrogen mobility, especially in non-stoichiometric regimes. For the Li2O stoichiometry, structural metrics and diffusivity trends are benchmarked against available ab initio and experimental data. For other Li–O compositions, no ab initio molecular dynamics or experimental data exist for amorphous or molten states; the only exception is the binary Li–D system, which serves as a limiting case of the ternary Li–O–D mixture. These results provide insight into hydrogen isotope behavior, structural frustration, and phase stability in fusion-relevant lithium-based materials.