First-principles calculations of structural, electronic, and optical properties of monolayer β-AsxP1-x

The theoretical prediction of blue phosphorus has driven research into buckled group-V structures, including arsenic (beta-As) and phosphorus (beta-P). Inspired by black arsenic-phosphorus, studies on buckled arsenic- phosphorus (beta-AsxP1-x) are emerging but remain limited. In this work, we investigate the structural, electronic, and optical properties of monolayer beta-AsxP1-x across different arsenic (As) compositions using density functional theory (DFT). By calculating the bandgap values of 1414 structures across 11 compositions, we predict the bowing parameter of the non-linear bandgap-composition relationship. Based on this, one representative structure per composition is selected for further calculations. Our results show that the lattice constants of these structures closely follow Vegard's Law. Monolayer beta-AsxP1-x exhibit indirect bandgaps, displaying a non- monotonic trend: initially decreasing and then gradually increasing. Consistent with this trend, the first absorptance peak exhibits a redshift followed by a slight blueshift, with strong near-ultraviolet and moderate visible absorption. These findings demonstrate that beta-AsxP1-x compounds exhibit composition-tunable optoelectronic properties, promising for ultraviolet and visible-light electronic devices.