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Title: The phase diagram and hardness of carbon nitrides

Novel superhard materials, especially those with superior thermal and chemical stability, are needed to replace diamond. Carbon nitrides (C-N), which are likely to possess these characteristics and have even been expected to be harder than diamond, are excellent candidates. Here we report three new superhard and thermodynamically stable carbon nitride phases. Based on a systematic evolutionary structure searches, we report a complete phase diagram of the C-N system at 0–300 GPa and analyze the hardest metastable structures. Surprisingly, we find that at zero pressure, the earlier proposed graphitic-C3N4 structure (P6-bar m2) is dynamically unstable, and we find the lowest-energy structure based on s-triazine unit and s-heptazine unit.
Authors:
 [1] ;  [2] ;  [1] ;  [1]
  1. Stony Brook Univ., NY (United States). Dept. of Geosciences and Center for Materials by Design, Inst. for Advanced Computational Science
  2. Stony Brook Univ., NY (United States). Dept. of Geosciences and Center for Materials by Design, Inst. for Advanced Computational Science; Moscow Inst. of Physics and Technology (Russian Federation); Northwestern Polytechnical Univ., Xi'an (China). School of Materials Science; Zhu, Qiang [Stony Brook Univ., NY (United States). Dept. of Geosciences and Center for Materials by Design, Inst. for Advanced Computational Science
Publication Date:
OSTI Identifier:
1184778
Grant/Contract Number:
SC0012704; EAR-1114313; DMR-1231586
Type:
Accepted Manuscript
Journal Name:
Scientific Reports
Additional Journal Information:
Journal Volume: 5; Journal ID: ISSN 2045-2322
Publisher:
Nature Publishing Group
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation; Government of the Russian Federation
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE