Insights into atomic-scale surface reconstruction of NiTi alloy induced by ion implantation

The present study employs Density Functional Theory simulation to investigate the atomic-scale surface reconstruction of NiTi alloy induced by ion implantation. A 2 × 2 × 2 supercell containing pre-existing defects was constructed to investigate lattice distortion and defect structure stability. Additionally, a symmetrical three-layer NiTi (110) slab model with a vacuum thickness of 15 Å was employed for electronic calculations, including density of states, electron density difference, and work function. The findings suggest that ion implantation results in an increased occurrence of point defects, including both vacancies and doping-related structures. When occupying the vacancy, non-metal N and C atoms induce more pronounced lattice distortions compared to the metal Cr atom. Moreover, by examining orbital hybridization and charge density differences, it was discovered that the implanted ions exhibit a chemisorption behavior when interacting with the Ni/Ti-SV point defect structure.