Hydrostatic (isotropic) strain engineering of optoelectronic and mechanical properties in lead-free inorganic antiperovskites Ba3PnBr3 (Pn = N, P, As, Sb)

We systematically investigate the strain-dependent structural, optoelectronic, charge carrier statistical, and mechanical properties of lead-free inorganic halide antiperovskites Ba 3 PnBr 3 (Pn = N, P, As, Sb) using density functional theory (DFT) calculations. Application of hydrostatic (isotropic) strain leads to significant modulation of the electronic and optical properties. Compressive strain from 2% to 6% reduces the band gap of Ba 3 PnBr 3 to a range of 0.11–0.75 eV (0.08–0.70 eV) without (with) spin-orbit coupling, resulting in a red shift of the absorption edge peaks. Tensile strain from 2% to 6% increases the band gap to values between 0.46–1.16 eV (0.44–1.08 eV), respectively, causing a corresponding blue shift. The HSE06 functional predicts direct electronic band gaps that increase monotonically under tensile strain, with values ranging from 0.624 to 1.115 eV for Ba 3 NBr 3 , 0.894 to 1.647 eV for Ba 3 PBr 3 , 0.919 to 1.710 eV for Ba 3 AsBr 3 , and 0.794 to 1.694 eV for Ba 3 SbBr 3 across the applied strain range of 6% to 6%. Analysis of charge carrier statistics reveals that the application of tensile strain significantly augments the p-type Seebeck coefficient, reaching magnitudes of approximately 560 V/K at 300 K in both Ba 3 PBr 3 and Ba 3 AsBr 3 , whereas compressive strain suppresses it. Consequently, these findings substantiate that pnictogen substitution, coupled with mechanical strain modulation, provides a robust mechanism for tailoring the electronic band gap, optical characteristics, and thermoelectric efficiency. This underscores the exceptional viability of these compounds for integration into advanced, strain-tunable optoelectronic and thermoelectric device architectures.