CN− and NH2− co-decorated graphdiynes: A theoretical investigation

Abstract

In this work, the cyano (CN−) and amino (NH2−) groups are used to co-decorate the monolayer graphdiyne (GDY) resulting in two new GDY derivative systems (i.e., A1C2- and A2C1-GDYs). The structural stabilities of these two systems are carefully verified. Due to the local dipole moments introduced by the CN− and NH2− groups, as well as the breaking central symmetry, the corresponding mechanical, piezoelectric, and electronic features, even the electrical transport properties, are significantly altered comparing with the pristine GDY, F-GDY, and CN-GDY systems. The predicted band gaps of A1C2- and A2C1-GDYs are around 1.25 eV and 1.33 eV at the PBE level, respectively, which are obviously larger than that of the pristine GDT monolayer (0.53 eV at the same theoretical level). There are also observable negative piezoelectric effects in both new GDY derivatives due to the change of the local dipole moment under strains. Moreover, the negative electrical conductivity constants σxy are revealed in both co-decorated monolayer GDY systems at certain chemical potentials, indicating the switch of the major carrier types according to the Hall effect. This theoretical study not only expands the GDY family, but also provides a new opportunity for switching carrier types in 2D materials using the in-plane electric field.