<p>In this work, first-principles calculations based on density functional theory (DFT) were performed using the VASP software package to optimize the geometric structures of terbium-related point defects in diamond. Thermodynamic stability evaluation via cohesive energy and defect formation energy confirmed that the TbV₂ color center possesses the most favorable atomic configuration. Electronic structure calculations were further carried out on this optimized geometry to characterize charge transfer and interatomic bonding between Tb and carbon atoms. By systematically analyzing the band structure, density of states, and spin–orbit coupling effects, the energy-level scheme of the diamond TbV₂ color center was established. The ⁷F_J manifold acts as the ground state, while the ⁵D₄ manifold corresponds to the excited state. The zero-phonon line (ZPL) energy for the radiative transition from the ⁵D₄ excited state to the ⁷F_J ground state was calculated as 2.28&#xa0;eV, corresponding to green fluorescence at a wavelength of 544&#xa0;nm. To systematically explore how nitrogen (N) and boron (B) dopants modulate the luminescence performance of TbV₂ color centers, all thermodynamically stable N-doped, B-doped, and N/B co-doped configurations were screened via cohesive and formation energy calculations. Subsequent electronic structure simulations were implemented to clarify the dependence of optical transition energy levels on dopant species and doping concentration on the basis of these stable defect geometries. Moreover, the ZPL positions and corresponding fluorescence wavelengths of various doped TbV₂ color centers were theoretically predicted. Our theoretical investigations verify that the diamond TbV₂ color center can serve as a high-performance single-photon source.</p>