Structural, mechanical, electronic, and optoelectronic properties of wide-band-gap hydride perovskite BaNaH3Pt from hybrid density functional theory

Lead-free wide-band-gap perovskites are actively sought for ultraviolet (UV) and visible optoelectronics with improved environmental compatibility. Here, we assess the structural stability and optoelectronic potential of the hydride perovskite BaNaH 3 Pt. First-principles density functional theory calculations were performed using GGA–PBE for structural optimization and elastic properties, and the HSE06 hybrid functional for electronic and optical properties of the optimized hexagonal P6₃/mmc phase. Lattice stability was examined using the Goldschmidt tolerance and octahedral factors, formation energy, and phonon calculations, and thermodynamic quantities were evaluated over 0–1000 K. The P6₃/mmc phase satisfies the Born mechanical stability criteria and exhibits no imaginary phonon modes, indicating mechanical and dynamical stability. The Voigt–Reuss–Hill averages (B = 23.1 GPa, G = 7.83 GPa) characterize BaNaH 3 Pt as a relatively soft solid with ductile tendencies. HSE06 predicts an indirect band gap of 2.4 eV with small and nearly symmetric electron and hole effective masses. The optical response shows a moderate static dielectric constant (ε₁(0) = 7), a low-absorption region below the main optical onset, and strong absorption at higher photon energies extending from the visible to the near-UV/UV, while the reflectivity remains moderate (R(0) = 0.18 and below 0.35 up to 10 eV). These results suggest that BaNaH 3 Pt is a promising lead-free hydride perovskite for visible-to-UV optoelectronic applications, including photodetection.