Monolayer Penta-BeAs: A Promising 2D Materials for Toxic Gas Sensor with High Selectivity.

The discovery of novel materials with high gas sensing selectivity is a key driver of gas sensor technology. Based on the recently reported two-dimensional (2D) pentagonal BeP, we introduce penta-BeAs as a new member of the pentagonal family of materials for toxic gas sensors based on density functional theory (DFT). For electronic applications, a band structure calculation showed that penta-BeAs has indirect band gaps of 0.38 and 0.79 eV, using GGA-PBE or HSE functionals. Stability analysis confirmed that penta-BeAs is dynamically, mechanically, and thermally stable. The adsorption of toxic gases (CO, NO, and NO) and nontoxic gases (H, N, HO, and CO) on the penta-BeAs monolayer was studied. The contrasting adsorption behavior observed between toxic and nontoxic gases on penta-BeAs (physisorption vs chemisorption) underscores its high selectivity for toxic gas-sensing applications. Adsorption energies for toxic gases fall within a moderate range (0.4-0.8 eV), indicating good reversibility and short recovery times at room temperature. Additionally, the quantum transport properties of penta-BeAs were studied using the nonequilibrium Green's function (NEGF) approach, confirming strong sensitivity and selectivity toward toxic gases.