Optical, Electronic Properties and Anisotropy in Mechanical Properties of “X” Type Carbon Allotropes

At a Glance

Metadata	Details
Publication Date	2020-05-01
Journal	Materials
Authors	Jiao Cheng, Qidong Zhang
Institutions	Xidian University, Xi’an University of Architecture and Technology
Citations	36
Analysis	Full AI Review Included

Technical Documentation & Analysis: Advanced Carbon Allotropes

Executive Summary

This documentation analyzes the first-principles calculation study of seven X-type carbon allotropes, including conventional diamond, focusing on mechanical, electronic, and optical properties. The findings validate the superior performance metrics of Single Crystal Diamond (SCD) and highlight the potential of other carbon structures for advanced semiconductor applications.

Benchmark Validation: The study confirms that conventional diamond exhibits the highest mechanical moduli (Bulk, Shear, Young’s) and the lowest elastic anisotropy (E_max/E_min ratio of 1.11) among all investigated allotropes, reinforcing its status as the premier material for extreme mechanical stability.
Electronic Structure: While diamond is confirmed as an indirect band gap semiconductor (E_g = 5.3 eV via HSE06), the research identifies TY carbon, T carbon, and Supercubane as potential direct band gap semiconductors, crucial for efficient photoelectric devices.
Photoelectric Potential: TY carbon, T carbon, and Cubane-diyne show optical absorption coefficients in the visible region comparable to or higher than GaAs, suggesting their utility in next-generation solar cells or photodetectors.
Thermal Stability: Diamond possesses the highest calculated Debye temperature (Θ_D = 2224.84 K), indicating superior thermal stability and high thermal conductivity, essential for high-power electronics.
Anisotropy Control: The study provides detailed anisotropy ratios for Young’s modulus, shear modulus, and sound velocity across major crystal planes, offering critical data for engineers designing devices sensitive to crystallographic orientation.

Technical Specifications

Extracted and calculated parameters for Diamond and key allotropes, based on first-principles DFT/HSE06 calculations.

Parameter	Value	Unit	Context
Lattice Parameter (a)	3.566	Å	Diamond (GGA calculation)
Bulk Modulus (B)	431	GPa	Diamond (Highest mechanical stability)
Young’s Modulus (E)	1116	GPa	Diamond
Shear Modulus (G)	522	GPa	Diamond
Elastic Anisotropy (E_max/E_min)	1.11	Ratio	Diamond (Lowest anisotropy)
Band Gap (E_g)	5.3	eV	Diamond (HSE06 Hybrid Functional)
Band Gap (E_g)	2.2	eV	TY Carbon (Direct Band Gap, HSE06)
Debye Temperature (Θ_D)	2224.84	K	Diamond (Highest thermal stability)
Mean Sound Velocity (v_m)	13,307	m/s	Diamond
Static Refractive Index (n(0))	1.9 to 2.3	N/A	Range for Cubane-diyne to Supercubane
Absorption Coefficient	> GaAs	N/A	C₁₀-C, C₂₄-C, TY Carbon (Visible region)

Key Methodologies

The research utilized advanced computational methods to predict material properties, ensuring high accuracy, particularly for electronic band gaps.

Density Functional Theory (DFT): All structural geometric optimization and physical property predictions were performed using DFT, as implemented in the Cambridge Sequential Total Energy Package (CASTEP).
Pseudopotentials and Minimization: Vanderbilt ultrasoft pseudopotentials were employed, coupled with the Broyden-Fletcher-Goldfarb-Shanno (BFGS) minimization scheme for structural optimization.
Exchange-Correlation Functionals:
- The Perdew-Burke-Ernzerhof (PBE) functional of the Generalized Gradient Approximation (GGA) was used for initial calculations and mechanical properties.
- The Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional was used to accurately predict electronic band gaps, correcting the known underestimation by standard DFT methods.
Convergence Criteria: High precision was maintained with strict convergence parameters:
- Plane-wave E_cutoff energy: 520 eV.
- Total energy convergence: within 0.001 eV/atom.
- Maximum ionic displacement: within 5 x 10^-4 Å.
- Maximum force on atom: 0.01 eV/Å.
- Maximum stress: 0.02 GPa.
Anisotropy Calculation: Mechanical anisotropy (Young’s modulus, shear modulus, Poisson’s ratio) was calculated using unit vectors defined by two angles (θ, φ) and a scanning angle (χ), providing detailed 3D contour plots.

6CCVD Solutions & Capabilities

The research confirms the fundamental superiority of diamond in mechanical stability, thermal properties, and wide band gap characteristics. 6CCVD provides the high-quality MPCVD diamond necessary to leverage these properties in real-world engineering and scientific applications.

Applicable Materials

To replicate or extend the research findings into functional devices, 6CCVD recommends the following materials:

Optical Grade Single Crystal Diamond (SCD): Required for applications demanding the lowest possible elastic anisotropy and highest mechanical strength, as validated by the paper. Our SCD offers Ra < 1nm polishing, crucial for minimizing surface defects that affect optical absorption and mechanical integrity.
Boron-Doped Diamond (BDD): Essential for exploring the semiconductor and photoelectric applications discussed. While the paper focuses on theoretical allotropes, BDD is the established material for diamond-based UV/deep-UV photodetectors and high-power electronics, leveraging diamond’s wide band gap (5.5 eV).
Polycrystalline Diamond (PCD) Substrates: For large-area applications (up to 125mm wafers) where high mechanical stiffness (high Young’s modulus) and thermal management are critical, 6CCVD PCD offers excellent performance validated by the mechanical data presented.

Customization Potential

The detailed analysis of crystal orientation and anisotropy (e.g., in the (111) plane vs. (100) plane) necessitates precise material control, which 6CCVD provides:

Research Requirement	6CCVD Customization Capability
Specific Crystal Orientation: Need to study properties along [100], [110], or [111] directions.	SCD plates available in various orientations (e.g., (100), (111)) with precise alignment for anisotropic studies.
Photoelectric Device Fabrication: Requires contact deposition for semiconductor testing.	In-house metalization services including Au, Pt, Pd, Ti, W, and Cu, allowing for custom electrode patterns and ohmic contacts.
Large-Scale Testing: Need for larger samples for mechanical or optical testing.	PCD wafers available up to 125mm diameter; SCD substrates available up to 10mm thickness.
Surface Quality for Optical Testing: Optical properties are highly sensitive to surface finish.	SCD polishing to Ra < 1nm and inch-size PCD polishing to Ra < 5nm, ensuring minimal scattering losses and high optical purity.

Engineering Support

The theoretical prediction of novel carbon allotropes (TY carbon, T carbon) as direct band gap semiconductors opens new avenues for research. 6CCVD’s in-house PhD team specializes in correlating theoretical predictions with practical MPCVD growth parameters. We can assist researchers in selecting the optimal material specifications (doping level, orientation, surface finish) for similar Wide Band Gap Semiconductor projects, ensuring the highest quality diamond platform for advanced device prototyping.

Call to Action: For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Based on first-principle calculations, the mechanical anisotropy and the electronic and optical properties of seven kinds of carbon materials are investigated in this work. These seven materials have similar structures: they all have X-type structures, with carbon atoms or carbon clusters at the center and stacking towards the space. A calculation of anisotropy shows that the order of elastic anisotropy in terms of the shear modulus, Young’s modulus and Poisson’s ratio of these seven carbon materials with similar structure is diamond < supercubane < T carbon < Y carbon < TY carbon < cubane-diyne < cubane-yne. As these seven carbon materials exhibit cubic symmetry, Young’s modulus has the same anisotropy in some major planes, so the order of elastic anisotropy in the Young’s modulus of these seven main planes is (111) plane < (001) plane = (010) plane = (100) plane < (011) plane = (110) plane = (101) plane. It is also due to the fact that their crystal structure has cubic symmetry that the elastic anisotropy in the shear modulus and the Poisson’s ratio of these seven carbon materials on the seven major planes are the same. Among the three propagation directions of [100], [110], and [111], the [110] propagation direction’s anisotropic ratio of the sound velocity of TY carbon is the largest, while the anisotropic ratio of the sound velocity of cubane-diyne on the [100] propagation direction is the smallest. In addition, not surprisingly, the diamond has the largest Debye temperature, while the TY carbon has the smallest Debye temperature. Finally, TY carbon, T carbon and cubane-diyne are also potential semiconductor materials for photoelectric applications owing to their higher or similar absorption coefficients to GaAs in the visible region.

Tech Support

Original Source

DOI: https://doi.org/10.3390/ma13092079

References

2020 - Prediction of a novel carbon allotrope from first-principle calculations: A potential superhard material in monoclinic symmetry [Crossref]
2020 - PBCF-graphene: A 2D sp2 hybridized honeycomb carbon allotrope with a direct band gap [Crossref]
2016 - Three dimensional metallic carbon from distorting sp3-Bond [Crossref]
2011 - T-Carbon: A novel carbon allotrope [Crossref]
2017 - Pseudo-topotactic conversion of carbon nanotubes to T-carbon nanowires under picosecond laser irradiation in methanol [Crossref]
2012 - Carbon allotropes with triple bond predicted by first-principle calculation: Triple bond modified diamond and T-carbon [Crossref]
2015 - C2/m-carbon: Structural, mechanical, and electronic properties [Crossref]
2020 - Five carbon allotropes from Squaroglitter structures [Crossref]
2019 - Two novel superhard carbon allotropes with honeycomb structures [Crossref]