First-principles insights into the electronic and optical behavior of ANiO3 perovskites with alkali and alkaline earth metal substitution

We present a systematic first-principles study of ANiO 3 perovskites (A = Li, Na, K, Rb, Be, Mg, Ca, Sr, Ba) to elucidate how A-site substitution governs their structural, electronic, and optical properties. Using hybrid density functional theory (PBE 0 and HSE 06 ), we evaluate lattice stability, band structures, density of states, and frequency-dependent optical functions, including absorption, reflectivity, refractive index, extinction coefficient, and energy loss spectra. Results reveal a progression from metallic or semimetallic behavior in LiNiO 3 , RbNiO 3 , and BeNiO 3 to wide-gap insulating states in SrNiO 3 and BaNiO 3 . PBE 0 consistently predicts larger bandgaps and closer agreement with experimental benchmarks compared to HSE 06 . Optical responses strongly correlate with electronic structure: alkali compounds display low-energy absorption and plasmonic peaks, while alkaline earth members show enhanced UV absorption and high dielectric response. These findings highlight A-site chemistry as an effective strategy for tailoring nickelate perovskites for optoelectronic, photonic, and energy-conversion applications.