Pressure-dependent electronic, optical, and mechanical properties of antiperovskite X3NP (X = Ca, Mg): A first-principles study

Abstract Hydrostatic pressure provides an efficient way to tune and optimize the properties of solid materials without changing their composition. In this work, we investigate the electronic, optical, and mechanical properties of antiperovskite X 3 NP (X 2+ = Ca, Mg) upon compression by first-principles calculations. Our results reveal that the system is anisotropic, and the lattice constant a of X 3 NP exhibits the fastest rate of decrease upon compression among the three directions, which is different from the typical Pnma phase of halide and chalcogenide perovskites. Meanwhile, Ca 3 NP has higher compressibility than Mg 3 NP due to its small bulk modulus. The electronic and optical properties of Mg 3 NP show small fluctuations upon compression, but those of Ca 3 NP are more sensitive to pressure due to its higher compressibility and lower unoccupied 3 d orbital energy. For example, the band gap, lattice dielectric constant, and exciton binding energy of Ca 3 NP decrease rapidly as the pressure increases. In addition, the increase in pressure significantly improves the optical absorption and theoretical conversion efficiency of Ca 3 NP. Finally, the mechanical properties of X 3 NP are also increased upon compression due to the reduction in bond length, while inducing a brittle-to-ductile transition. Our research provides theoretical guidance and insights for future experimental tuning of the physical properties of antiperovskite semiconductors by pressure.