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 (β-As) and phosphorus (β-P). Inspired by black arsenic-phosphorus, studies on buckled arsenic-phosphorus (β-As_xP_1-x) are emerging but remain limited. In this work, we investigate the structural, electronic, and optical properties of monolayer β-As_xP_1-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 β-As_xP_1-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 β-As_xP_1-x compounds exhibit composition-tunable optoelectronic properties, promising for ultraviolet and visible-light electronic devices.