Detailed Analysis of the Electronic and Structural Properties of the New Compound Tl₁₋ₓBx P, Taking into Account the Spin–Orbit Effect Using MBJ-GGA

We report an ab initio study of ternary Tl₁₋ₓBₓP alloys (x = 0.25, 0.5) in the zinc-blende structure using DFT with GGA and mBJ-GGA, including spin–orbit coupling (SOC). A 2×2×2 supercell based on TlN was used, where boron atoms were substituted by thallium. Our results show that while BP is an indirect semiconductor and TlN is metallic, Tl₁₋ₓBₓP alloys exhibit a semi-metallic character, bridging wide-gap borides and narrow-gap thallium compounds. Increasing boron content reduces the lattice constants and modifies the total energy, enabling precise tuning of electronic properties. This work highlights the stabilizing role of thallium in forming new alloy phases and provides a novel route for band-gap engineering in III–V semiconductors, considering SOC effects. These findings offer guidance for the design of future optoelectronic and electronic devices.