Prediction of two-dimensional nodal-line semimetals in a carbon nitride covalent network

Haiyuan Chen, Shunhong Zhang, Wei Jiang, Chunxiao Zhang, Heng Guo, Zheng Liu, Zhiming Wang, Feng Liu, Xiaobin Niu

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42 Scopus citations

Abstract

Carbon nitride covalent compounds have emerged as a prominent member of 2D materials beyond graphene. The experimental realizations of 2D graphitic carbon nitride g-C3N4, nitrogenated holey graphene C2N, and polyaniline C3N have shown their promising potential in energy and environmental applications. In this work, we predict a new type of carbon nitride network with a C9N4 stoichiometry from first principles calculations. Unlike common C-N compounds and covalent organic frameworks (COFs), which are typically insulating, surprisingly C9N4 is found to be a 2D nodal-line semimetal. The nodal line in C9N4 forms a closed ring centered at the Γ point, which originates from the pz orbitals of both C and N. The linear crossing occurs right at the Fermi level contributed by two sets of dispersive Kagome and Dirac bands, which is robust due to negligible spin-orbit coupling in C and N. Furthermore, it is revealed that the degeneracy along the high-symmetry path is protected by out-of-plane mirror or C2 rotational symmetry, rather than in-plane mirror symmetry. The chemical potential difference between C and N, as validated by using a single orbital tight-binding model, plays a significant role in forming the nodal ring. Interestingly, a new structure of the nodal line, i.e., a nodal cylinder, is found in momentum space for AA-stacked C9N4. Our results indicate possible functionalization for a novel metal-free C-N covalent network with interesting semimetallic properties.

Original languageEnglish (US)
Pages (from-to)11252-11259
Number of pages8
JournalJournal of Materials Chemistry A
Volume6
Issue number24
DOIs
StatePublished - 2018
Externally publishedYes

Bibliographical note

Funding Information:
X. N. acknowledges the financial support from the Recruitment Program of Global Young Experts of China and Sichuan one thousand Talents Plan. F. L. acknowledges the support from the US-DOE (Grant No. DE-FG02-04ER46148). H.C. acknowledges the financial support from the Graduate School of UESTC. S. Z. is supported by the National Postdoctoral Program for Innovative Talents of China (BX201600091) and the funding from the China Postdoctoral Science Foundation (2017M610858). The computational resources are provided by the CHPC at the University of Utah and the National SuperComputer Center in Tianjing, China.

Funding Information:
X. N. acknowledges the nancial support from the Recruitment Program of Global Young Experts of China and Sichuan one thousand Talents Plan. F. L. acknowledges the support from the US-DOE (Grant No. DE-FG02-04ER46148). H.C. acknowledges the nancial support from the Graduate School of UESTC. S. Z. is supported by the National Postdoctoral Program for Innovative Talents of China (BX201600091) and the funding from the China Postdoctoral Science Foundation (2017M610858). The computational resources are provided by the CHPC at the University of Utah and the National SuperComputer Center in Tianjing, China.

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