Novamene - A new class of carbon allotropes

At a Glance

Metadata	Details
Publication Date	2017-02-01
Journal	Heliyon
Authors	Larry A. Burchfield, Mohamed Al Fahim, Richard S. Wittman, Francesco Delodovici, Nicola Manini
Institutions	Pacific Northwest National Laboratory, Battelle
Citations	34
Analysis	Full AI Review Included

Novel Carbon Allotrope Analysis: Novamene (sp²/sp³ Hybrid Structures)

Executive Summary

The reported computational study introduces Novamene, a theoretically stable class of carbon allotropes characterized by a unique structural blend of conductive sp² carbon (graphene/fusenes) core surrounded by insulating sp³ hexagonal diamond (lonsdaleite) shells. This hybrid architecture positions Novamene as a pivotal material for next-generation microelectronics.

Novel Structure: Novamene combines the electronic conductivity of sp² rings with the high stiffness and dielectric properties of sp³ diamond, offering a built-in insulator-conductor framework.
Electronic Properties: Density Functional Theory (DFT) simulations confirm the single-ring novamene structure is a stable, small-gap semiconductor (0.34 eV indirect gap), suggesting potential applications in transistors and energy harvesting.
Electronic Transport: The central sp² graphene core facilitates high carrier mobility, while the surrounding sp³ lonsdaleite shell provides insulation and structural integrity, crucial for integrated circuits.
Structural Stability: Despite being marginally less stable than graphite or cubic diamond, the single-ring novamene structure represents a sharp local energy minimum, guaranteeing long-term stability.
Experimental Relevance: The predicted 77% sp³ fraction aligns closely with experimental data from synthesized Q-carbon, suggesting Novamene may be a fundamental crystalline constituent in amorphous carbon films.
Target Applications: Predicted uses include advanced electronic components (transistors, integrated circuits), optoelectronics, Hall effect sensors, and high-efficiency solar absorbers due to strong infrared light absorption.

Technical Specifications

The following structural and electronic parameters were determined via DFT-LDA simulations for the lowest-energy dimerized single-ring novamene structure (52 atoms per cell).

Parameter	Value	Unit	Context
Lattice Constant (a)	8.4188	Å	Hexagonal lattice parameter
Lattice Constant (c)	4.9981	Å	Hexagonal lattice parameter
Atoms per Cell (N)	52	atoms	ABA’B’ dimerized structure (minimum repeated unit)
Cell Volume	306.79	Å³	Theoretical cell volume for the 52-atom unit
Density (Calculated)	3381	kg/m³	High density, similar to Lonsdaleite (3638 kg/m³)
Cohesive Energy	9.930	eV/atom	Indicates thermodynamic stability (local energy minimum)
Electronic Band Gap (E_g)	0.34	eV	Indirect gap, characterizes the small-gap semiconductor phase
Sp³ Carbon Fraction	77	%	Comparable to experimental Q-carbon composition (75%-85%)
Energy Barrier (Metallic vs. Semiconducting)	0.042	eV/atom	Energy difference between the undistorted metallic phase and the dimerized semiconducting ground state
Simulation Method	DFT-LDA	N/A	Density Functional Theory - Local Density Approximation

Key Methodologies

The theoretical synthesis and characterization of single-ring novamene were performed using high-level quantum mechanical calculations, providing the structural groundwork for potential experimental synthesis.

Structural Concept Formulation: Novamene was conceptualized as sp² hexagonal carbon rings (fusenes) enveloped by sp³ hexagonal diamond (lonsdaleite), leveraging the insulating/conducting contrast.
Initial Cell Construction: A tentative structure was constructed enforcing threefold symmetry around the sp² core, initially resulting in a 26-atom periodic cell (A and B planes) with an AB interplanar distance of 2.5 Å.
DFT Setup: Density Functional Theory (DFT) calculations were performed using the Local Density Approximation (LDA) to predict the equilibrium structure.
Computational Tools: Simulations utilized the Quantum Espresso package with a plane-waves basis set. Standard ultrasoft pseudopotentials were applied to account for the carbon 1s core electrons.
Kinetic Energy Cutoff: A high kinetic energy cutoff of 408 eV was employed to ensure accuracy in the plane-waves basis expansion.
Atomic and Cell Relaxation: Atomic positions and cell parameters were fully relaxed to identify the lowest energy local minimum (the dimerized semiconducting structure). Relaxation thresholds were stringent:
- Forces: Equal to or less than 4 pN.
- Residual Stress: Less than 10 bar.
- Total Energy Convergence: Less than 10^-6 eV/atom.
Theoretical Characterization: Theoretical electronic band structures, density of states (DOS), and X-ray Diffraction (XRD) patterns (using λ = 154 pm, Cu K_α) were calculated for future experimental comparison.

6CCVD Solutions & Capabilities

The Novamene research highlights the continuous need for high-quality, highly controlled CVD diamond materials, particularly those relating to sp³ hexagonal diamond (lonsdaleite) and advanced electronic applications. 6CCVD is an expert partner capable of supplying the foundational materials and advanced customization required to synthesize, characterize, and utilize these novel carbon allotropes.

Research Requirement	6CCVD Specialized Solution	Technical Rationale & Customization
Crystalline Sp³ Foundation	High-Purity Single Crystal Diamond (SCD)	Novamene’s structure relies heavily on hexagonal diamond (lonsdaleite), an sp³ phase. Our Optical Grade SCD offers the highest purity and minimal lattice defects, essential for synthesizing or modeling the ideal sp³ component necessary to stabilize Novamene.
Controlled Hybridization/Defects	Custom Grade Polycrystalline Diamond (PCD) Plates	The experimental synthesis of Q-carbon/Novamene often involves thin films or mixed-phase growth. We provide PCD wafers up to 125 mm in diameter with controlled grain sizes, which can be tailored for experiments focusing on managing the sp²-sp³ interface and defect density.
Advanced Electronic Substrates	Ultra-Smooth SCD and PCD Polishing (Ra < 1 nm)	Thin film deposition, structural analysis, and electronic measurements require extremely flat surfaces. 6CCVD provides state-of-the-art polishing: Ra < 1 nm for SCD and Ra < 5 nm for inch-size PCD, ensuring an ideal foundation for Novamene synthesis.
Semiconductor Interface Development	Boron-Doped Diamond (BDD) Wafers	Since Novamene is predicted to be a semiconductor (0.34 eV gap), controlled doping is crucial for device integration. 6CCVD supplies BDD material in various thicknesses (0.1 µm to 500 µm) and doping levels to create highly conductive, stable electrodes for transistor or sensor applications.
Device Integration and Bonding	Custom Metalization Services	Research on Novamene’s electronic properties (transport, switching) requires precise contact formation. We offer in-house metalization including Ti, Pt, Au, Pd, W, and Cu patterns, fabricated to custom engineering specifications.
Material Sizing and Geometry	Custom Dimensions and Thicknesses	Whether replicating the theoretical unit cell or scaling up for device testing, 6CCVD provides custom cuts and specific material thicknesses for SCD and PCD, ranging from 0.1 µm films up to 10 mm substrates. Global shipping (DDU/DDP) is available.

Engineering Support

6CCVD’s in-house team of PhD material scientists stands ready to assist researchers and engineers focused on novel carbon allotropes, phase transitions (e.g., Q-carbon, lonsdaleite formation), and optimizing CVD parameters for specific sp²-sp³ hybridization targets. We specialize in translating theoretical concepts into manufacturable diamond materials.

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

View Original Abstract

We announce a new class of carbon allotropes. The basis of this new classification resides on the concept of combining hexagonal diamond (sp3 bonded carbon - lonsdaleite) and ring carbon (sp2 bonded carbon - graphene). Since hexagonal diamond acts as an insulator and sp2 bonded rings act as conductors, these predicted materials have potential applications for transistors and other electronic components. We describe the structure of a proposed series of carbon allotropes, novamene, and carry out a detailed computational analysis of the structural and electronic properties of the simplest compound in this class: the single-ring novamene. In addition, we suggest how hundreds of different allotropes of carbon could be constructed within this class.

Tech Support

Original Source

DOI: https://doi.org/10.1016/j.heliyon.2017.e00242

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