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Abstract <p>A novel carbon allotrope, hexagonal C<sub>8</sub>, is proposed from crystal chemistry and quantum density functional theory (DFT) investigations of the ground state structures and pertaining physical properties. The structure possessing an unknown topology with 3,4<sup>2</sup>-c net exhibits corner sharing tetrahedra connected by cyclopropane-like C<sub>3</sub>. C<sub>8</sub> was subsequently used as a template to devise original binary subnitride C<sub>6</sub>N<sub>2</sub>. Both the allotrope and the binary phase were found cohesive and stable mechanically (elastic constants and their combinations) and dynamically (phonons band structures) whilst presenting large hardness: <i>H</i><sub>V</sub>(C<sub>8</sub>) = 60 GPa, and <i>H</i><sub>V</sub>(C<sub>6</sub>N<sub>2</sub>) = 49 GPa. The electronic band structure reveals conductive behavior for the allotrope and insulating one for C<sub>6</sub>N<sub>2</sub> with <i>E</i><sub>gap</sub> ∼ 3 eV.</p>

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Superhard Novel C8 Allotrope and Derived Subnitride C6N2 with Cyclopropane-Like C3 Building Units. Crystal Chemistry and First Principles Investigations

  • 期刊论文

  • 发表日期：

    2025年2月1日

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  • Samir F Matar

摘要

Abstract

A novel carbon allotrope, hexagonal C8, is proposed from crystal chemistry and quantum density functional theory (DFT) investigations of the ground state structures and pertaining physical properties. The structure possessing an unknown topology with 3,42-c net exhibits corner sharing tetrahedra connected by cyclopropane-like C3. C8 was subsequently used as a template to devise original binary subnitride C6N2. Both the allotrope and the binary phase were found cohesive and stable mechanically (elastic constants and their combinations) and dynamically (phonons band structures) whilst presenting large hardness: HV(C8) = 60 GPa, and HV(C6N2) = 49 GPa. The electronic band structure reveals conductive behavior for the allotrope and insulating one for C6N2 with Egap ∼ 3 eV.