Electronic and optical properties of lithium-decorated δ-graphyne from first principles

• Published in: Optik (Stuttgart) 2020-08, Vol.216, p.164898, Article 164898
• Main Authors: Qin, Xue-Fang, Shao, Zhi-Gang, Wang, Cang-long, Yang, Lei
• Format: Article
• Language: English
• Subjects: Electronic and optical properties; First-principle; Li decorated; δ-graphyne
• ISSN: 0030-4026; 1618-1336
• DOI: 10.1016/j.ijleo.2020.164898

•Two stable Li-doped δ-graphyne structures exhibit metallic electronic structures.•Optical properties of three δ-graphynes exhibit strong anisotropic behaviour.•The reflectivity under parallel polarization is significant greater than the counterpart value under vertical polarization.•Three δ-graphyne structures have broad frequency photoresponse ranging from the zero frequency to ultra-violet regimes. First-principles calculations have been carried out to investigate the electronic and optical properties of lithium (Li)-decorated δ-graphynes. By calculating the total energy of different Li-decorated δ-graphyne structures, two most stable δ-graphyne structures are selected for this research, which are named δ1-graphyne and δ2-graphyne, respectively. Our results show that pristine δ-graphyne has two Dirac cones, while both δ1-graphyne and δ2-graphyne exhibit metallic character. The dielectric function, reflectivity, and absorption spectrum under different polarization conditions have been calculated to explore the optical properties of δ-graphyne, δ1-graphyne, and δ2-graphyne. The optical properties of three δ-graphyne structures all show strong anisotropic behaviour under different polarization directions. The reflectivity under Ex and Ey polarizations is significant greater than the counterpart value under the Ez polarization. In the parallel polarization, three δ-graphyne structures all have high reflectivity in a wide frequency range. Besides, strong absorption coefficients of three δ-graphyne structures exist from far infrared to high-frequency range under Ex and Ey polarizations. Our results reveal that three δ-graphyne structures have broad frequency photoresponse ranging from zero frequency to ultraviolet regimes, suggesting that δ-graphyne is a promising material for optoelectronics applications.