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6CCVD Research

A New Superhard sp3-Hybridized Carbon Allotrope with Ultrawide Direct Band Gap - Ibca-C64

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2025-09-15
JournalMaterials
AuthorsXinyu Wang, Qun Wei, Jing Luo, Meiguang Zhang, Bing Wei
InstitutionsBaoji University of Arts and Sciences, Xidian University
AnalysisFull AI Review Included

Executive Summary

Section titled “Executive Summary”

The research proposes Ibca-C64, a novel all-sp3 hybridized carbon allotrope, predicted via first-principles calculations, offering a unique combination of extreme mechanical strength and favorable electronic properties.

  • Dual Performance: Ibca-C64 is classified as a superhard semiconductor, exhibiting a Vickers hardness of 83.9 GPa (near-diamond) coupled with a wide direct band gap of 5.58 eV.
  • Electronic Advantage: The direct band gap overcomes the primary limitation of most existing sp3 superhard carbons, which typically possess indirect band gaps, restricting their use in optoelectronic applications.
  • Structural Stability: The orthorhombic structure is confirmed to be both mechanically stable (satisfies Born criteria) and dynamically stable (positive phonon frequencies across the Brillouin zone).
  • Synthesizability: The material exhibits favorable thermodynamic metastability, with a low relative energy difference of only 0.295 eV/atom above diamond, suggesting high potential for synthesis via high-pressure or plasma-based routes.
  • High Density: The calculated density is 3.465 g/cm3, only 0.08 g/cm3 less than diamond, indicating strong resistance to compression and shear deformation.
  • Anisotropy: Analysis of Young’s and torsional shear moduli confirms significant elastic anisotropy, providing critical guidance for directional design to prevent overload along weaker crystallographic orientations.

Technical Specifications

Section titled “Technical Specifications”
ParameterValueUnitContext
Vickers Hardness (Hv)83.9GPaEstimated via Chen’s empirical model.
Band Gap (Eg)5.58eVWide, direct band gap (calculated using HSE06 functional).
Relative Energy0.295eV/atomEnergy difference above diamond (metastability indicator).
Density (ρ)3.465g/cm3High density, comparable to diamond (3.517 g/cm3).
Crystal SystemOrthorhombicN/ASpace Group: Ibca-C64.
Atoms per Unit Cell64N/AFully sp3 hybridized structure.
Bulk Modulus (B)409GPaResistance to hydrostatic compression.
Shear Modulus (G)473GPaResistance to shear deformation.
B/G Ratio0.86N/AIndicates brittle mechanical nature (close to diamond’s 0.83).
Minimum Tensile Strength49.5GPaOccurs along the [111] direction.
Lowest Shear Strength42.1GPaOccurs in the (010)[001] orientation (dominant failure mechanism).
Lattice Parameter a4.525AngstromUnit cell dimension.
Lattice Parameter b8.667AngstromUnit cell dimension.
Lattice Parameter c9.394AngstromUnit cell dimension.

Key Methodologies

Section titled “Key Methodologies”

The prediction and characterization of Ibca-C64 were conducted entirely through first-principles calculations based on Density Functional Theory (DFT).

  1. Structure Prediction: The novel structure was proposed using the RG2 (Space Group and Graph Theory) method, constrained to orthorhombic symmetry and sp3 hybridization (four bonds per carbon atom).
  2. DFT Implementation: Calculations were performed using the Vienna Ab initio Simulation Package (VASP 5.4.4) employing the Projector Augmented Wave (PAW) method.
  3. Exchange-Correlation Functional: The Perdew-Burke-Ernzerhof (PBE) functional under the Generalized Gradient Approximation (GGA) was used for structural optimization and mechanical property calculations.
  4. Electronic Structure Calculation: The electronic band structure was calculated using the Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional to ensure accurate determination of the wide band gap.
  5. Convergence Parameters: A high cutoff energy of 900 eV was applied for plane-wave expansion. Total energy convergence was ensured within a strict tolerance of 1 x 10-5 eV/atom.
  6. Dynamical Stability: Phonon spectra were calculated using the PHONOPY package on a 2 x 1 x 1 supercell (128 atoms) to confirm the absence of imaginary frequencies, verifying dynamical stability.
  7. Mechanical Analysis: Elastic constants were calculated to confirm mechanical stability (Born criteria) and derive bulk/shear moduli using the Voigt-Reuss-Hill approximation. Vickers hardness was estimated using Chen’s empirical model.

Commercial Applications

Section titled “Commercial Applications”

The unique combination of superhardness and a wide direct band gap positions Ibca-C64 for high-performance applications in extreme environments.

  • Deep-Ultraviolet (DUV) Optoelectronics:
    • Ideal for DUV light-emitting diodes (LEDs), lasers, and photodetectors due to the wide direct band gap (5.58 eV).
    • Suitable for applications requiring operation in the DUV region, such as sterilization, sensing, and advanced lithography.
  • Extreme Abrasive and Cutting Tools:
    • Used in industrial cutting, drilling, and grinding applications where extreme hardness (83.9 GPa) is required.
    • Potential replacement or supplement for diamond in specific high-temperature or iron-based material machining processes where diamond performance is limited.
  • Wear-Resistant Electronic Components:
    • Development of durable, protective coatings for microelectronic devices operating under high stress or abrasive conditions.
    • Materials for high-power, high-frequency electronic devices requiring both mechanical integrity and semiconducting properties.
  • High-Pressure/High-Temperature Materials:
    • The high stability and density make it suitable for components used in extreme pressure or temperature environments, such as anvils or specialized reactor linings.
View Original Abstract

A novel all-sp3-hybridized superhard carbon allotrope, Ibca-C64, is proposed based on first-principles calculations combined with the RG2 (space group and graph theory) structure search method. A systematic investigation of its stability, mechanical properties, and electronic structure is performed. The results indicate that the energy difference between Ibca-C64 and diamond is only 0.295 eV/atom, suggesting its metastability. Detailed analysis of its elastic constants and phonon spectrum confirms both mechanical and dynamical stability. The Ibca-C64 structure demonstrates exceptional mechanical performance, with a Vickers hardness of 83.9 GPa. Furthermore, it possesses a wide direct band gap of 5.58 eV, indicating that Ibca-C64 is a superhard semiconductor material with outstanding mechanical properties.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 1990 - Solid C60: A new form of carbon [Crossref]
  2. 1991 - Helical microtubules of graphitic carbon [Crossref]
  3. 2007 - The rise of graphene [Crossref]
  4. 2014 - Graphdiyne and graphyne: From theoretical predictions to practical construction [Crossref]
  5. 2018 - Hybrid materials of 1D and 2D carbon allotropes and synthetic π-systems [Crossref]
  6. 2013 - First-principles structural design of superhard materials [Crossref]
  7. 2020 - Symmetry-guaranteed ideal Weyl semimetallic phase in face-centered orthogonal C6 [Crossref]
  8. 2018 - Computational discovery of a new rhombohedral diamond phase [Crossref]
  9. 2018 - Tetragon-based carbon allotropes T-C8 and its derivatives: A theoretical investigation [Crossref]

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