Atomic structures and electronic properties of Ta-doped 2H-NbSe₂

Chemical doping represents one of the most effective ways to precisely modulate material performances for target technological applications. Here, we report, by first-principles calculations, the impact of Ta doping on the crystal structures and electronic properties of the technologically relevant 2H-NbSe₂. We have considered a total of three Ta-doping models and demonstrated that the most thermodynamically stable one is that where the Ta atoms are located at the center of the octahedra comprised of Se atoms. Further structural analysis uncovers that the Ta-doped 2H-NbSe₂ maintains the original structure, yet shows an enhanced electronic property, which may be beneficial to the realization of the superconducting nature of 2H-NbSe₂. We also find hybridization of the Ta 5d and Se 4p orbitals and a marked degree of charge transfer between Ta and Se, forming a strong covalency of the Ta-Se bonds. Moreover, we also find that the tensile strain can remarkably enhance charge transfer in this system. Our calculations suggest that transition-metal doping will serve as a useful way to tailor the electronic structures of 2H-NbSe₂ so as to improve its electronic properties.