Structural differences in titanium surfaces under low-energy hydrogen ion irradiation: a molecular dynamics and topological data analysis approach

Abstract Microscopic structural changes on Ti surfaces under low-energy (≤30 eV) and perpendicular hydrogen ion (H + , H 2 + ) irradiation were investigated using molecular dynamics simulations and topological data analysis. Under H 2 + irradiation, H retention peaked at 5–7 eV, while H + irradiation decreased monotonically with increasing energy. Detailed analysis for H 2 + irradiation revealed that the retention ratio of two hydrogen atoms composing the H 2 molecule followed a similar trend. Persistence diagrams showed additional ring structures formed by H incorporation, leaving the original Ti ring framework intact. Most new rings comprised one H atom and two Ti atoms, with H-Ti distances contracting at lower irradiation energies. The centers of these rings shifted to shallower regions of the Ti surface with decreasing irradiation energy. These findings underscore the potential of low-energy hydrogen ion irradiation for controlled H incorporation into Ti surfaces, suggesting the atomic-level control of plasma-assisted surface engineering.