New SubmissionSulfur Vacancy–Induced Electronic and Topological Modifications in Ta₃S_2-_δ

Ta₃S₂ is a promising type-II Weyl semimetal, yet the effects of sulfur non-stoichiometry remain poorly understood. Using density functional theory (DFT), we investigate how sulfur vacancies in Ta₃S_2-δ influence structural stability, electronic structure, and topological properties. We calculate defect formation energies under varying chemical potentials and track their impact on Fermi-level position, carrier type, and band dispersion. Our results show that S vacancies introduce effective electron doping, shifting the Fermi level and altering the density of states near the Weyl nodes. Berry curvature and topological features evolve sensitively with δ, indicating that controlling sulfur content is crucial to preserve the material’s semimetallic character and optimize its transport properties.