Stable configurations and electronic structures of hydrogenated graphyne

Abstract

First-principles calculations are performed to investigate dynamical stability of hydrogenated graphyne and its electronic structures. We find that the zero point energy (ZPE) is important in evaluating the stability of hydrogenated graphyne. Based on the results of formation enthalpy, the hydrogenated configuration with only sp3 carbon atoms (eHH) is more stable than that with each carbon atom passivated by single hydrogen atom (eH). However, the Helmholtz free energy as functions of temperature indicates that eH is more favorable than eHH below 670K. Based on DFT-based phonon spectrum calculations, the dynamical stability of eHH and eH is confirmed. Of particular interest is that the band-gap feature of graphyne undergoes direct–indirect–direct transition with the increase in the concentration of hydrogen. The results indicate that eHH is favorable for the applications in the field of deep ultraviolet light-emitting devices.