Elastic, electronic and optical properties of stable pentagonal ZnO2

Abstract

Using first-principles calculations, we predict the existence of two dimensional (2D) pentagonal ZnO2 (penta-ZnO2) sheet and confirm that penta-ZnO2 is dynamically and mechanically stable. Due to its unique atomic configuration, penta-ZnO2 has intrinsic negative Possion's ratio, contrary to the most existing materials. Furthermore, Penta-ZnO2 is much more flexible than graphene-like ZnO and penta-graphene in elasticity. Using the Heyd-Scuseria-Ernzerhof (HSE06) functional, the calculated indirect energy band gap is 4.53eV, which is corresponding with optical gap (4.54eV). More interesting, in the visible range of light, we find that penta-ZnO2 has very low reflectance (0.0035%). Together with the expected zero absorption below the band gap, the light transmittance of penta-ZnO2 is almost 100% in a broad spectral range. Our study demonstrates that penta-ZnO2 possesses unique stable structure and promising mechanical, electronic and optical properties, which offers great potential in a wide range of applications in optoelectronics. Especially, the high flexibility and high light transmission make the penta-ZnO2 to be a promising candidate for transparent electrodes.