Theoretical study of the stability and formation methods of layer diamond-like nanostructures
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-01-01 |
| Journal | Letters on Materials |
| Authors | V. A. Greshnyakov, E. A. Belenkov |
| Institutions | Chelyabinsk State University |
| Citations | 5 |
| Analysis | Full AI Review Included |
Theoretical Study of Layer Diamond-Like Nanostructures
Section titled âTheoretical Study of Layer Diamond-Like NanostructuresâExecutive Summary
Section titled âExecutive SummaryâThis theoretical study (using Density Functional Theory) investigates the structure, stability, and formation of two novel two-dimensional (2D) diamond-like carbon bilayers, DL3-12 and DL4-6-12.
- Novel Materials: The study confirms the viability of two new sp3-hybridized 2D carbon structures, DL3-12 and DL4-6-12, derived from specific graphene polymorphs (L3-12 and L4-6-12).
- Semiconducting Properties: Both bilayers are predicted to be direct band gap semiconductors, with band gaps of 1.7 eV (DL3-12) and 2.3 eV (DL4-6-12).
- High Density: The calculated surface densities (0.082-0.098 ”g/cm2) are 7-28% greater than that of hexagonal graphene, indicating a highly compact structure.
- Porous Structure: Despite high density, the structures contain pores with a maximum diameter of approximately 4.5 Angstrom.
- Synthesis Route: The most probable formation method is strong uniaxial compression of two parallel graphene layers (AA stacking), mimicking known synthesis mechanisms for diamond-like materials.
- Stability Limits: The structures exhibit thermal stability up to 200 K (DL3-12) and 210 K (DL4-6-12), suggesting low-temperature synthesis is required.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Structure Type | Bilayer, Hexagonal | N/A | sp3-hybridized diamond-like carbon |
| Lattice Parameter (DL3-12) | 5.8204 | Angstrom | Unit cell dimension (a=b) |
| Lattice Parameter (DL4-6-12) | 7.5116 | Angstrom | Unit cell dimension (a=b) |
| Surface Density (DL3-12) | 0.082 | ”g/cm2 | 7% greater than hexagonal graphene |
| Surface Density (DL4-6-12) | 0.098 | ”g/cm2 | 28% greater than hexagonal graphene |
| Maximum Pore Diameter | ~4.5 | Angstrom | Characteristic of the porous structure |
| Direct Band Gap (DL3-12) | 1.7 | eV | Semiconductor property |
| Direct Band Gap (DL4-6-12) | 2.3 | eV | Semiconductor property |
| Thermal Stability Limit (DL3-12) | 200 | K | Temperature threshold before destruction |
| Thermal Stability Limit (DL4-6-12) | 210 | K | Temperature threshold before destruction |
| Formation Pressure (DL3-12) | > 16.7 | GPa | Required for phase transition from L3-12 graphene |
| Formation Pressure (DL4-6-12) | 8.6 | GPa | Required for phase transition from L4-6-12 graphene |
| Bilayer Thickness (h) | 1.5747 to 1.5946 | Angstrom | Varies slightly between the two structures |
Key Methodologies
Section titled âKey MethodologiesâThe research utilized computational methods to predict the structure and properties of the new 2D materials:
- Initial Structure Modeling: The diamond-like bilayers (DL3-12 and DL4-6-12) were modeled by cross-linking two identical layers of polymorphic hexagonal graphene (L3-12 or L4-6-12).
- Semi-Empirical Optimization: Initial geometric optimization of the modeled structures was performed using the PM7 semi-empirical method.
- First-Principle Calculation (DFT): Final geometric optimization and property calculations were conducted using Density Functional Theory (DFT) via the Quantum ESPRESSO software package.
- Exchange-Correlation Functional: The Perdew-Burke-Ernzerhof (PBE) formulation was used for the exchange-correlation energy functional.
- Basis Set Cutoff: An energy cutoff of 800 eV was applied to limit the dimensionality of the basis set.
- Brillouin Zone Integration: Integration was performed using k-point grids of 16x16x8 for structural calculations and 8x8x4 for molecular dynamics simulations.
- Simulated Synthesis (Compression): Phase transitions were modeled under uniaxial compression of the graphene precursors (L3-12 or L4-6-12) to determine the critical pressure required for bilayer formation.
- Thermal Stability Simulation: Annealing simulations were performed using molecular dynamics (1 fs time step) at temperatures near the stability limits (200 K and 210 K) to assess thermal robustness.
Commercial Applications
Section titled âCommercial ApplicationsâThe unique combination of semiconducting behavior, high density, and porous structure makes these materials promising for advanced technological applications:
- Nanoelectronics: As direct band gap semiconductors, DL3-12 and DL4-6-12 could serve as active components in next-generation 2D electronic devices, potentially replacing or complementing silicon in certain applications.
- Solar Energy: The materials are suitable for use in solar cells and photovoltaic devices, leveraging their semiconducting properties for efficient light absorption and charge separation.
- Molecular Sieves/Filtration: The presence of uniform pores (approximately 4.5 Angstrom diameter) suggests potential use as molecular sieves, gas separation membranes, or highly selective filters.
- Hydrogen Storage: Carbon nanostructures with high surface area and specific pore geometries are often investigated as hydrogen adsorbents, making these bilayers relevant for energy storage research.
- High-Pressure Synthesis: The study provides critical pressure thresholds (8.6 GPa and 16.7 GPa) necessary for synthesizing these novel diamond-like phases, guiding experimental high-pressure material synthesis efforts.
View Original Abstract
In this article, a theoretical study of the structure, stability, electronic properties and formation process of new two-dimensional diamond-like DL3-12 and DL4â6â12 nanostructures is carried out using the density functional theory method. As a result of the calculations, it is established that the structures of these diamond-like bilayers can be obtained in the process of model cross-linking of two identical graphene L3-12 or L4â6â12 layers. The DL3-12 and DL4â6â12 bilayers have hexagonal unit cells with the lattice parameters of 5.8204 and 7.5116 Ă , respectively. The calculated surface density of DL3-12 and DL4â6â12 bilayers is 0.082 and 0.098 ÎŒg / cm2, respectively, and exceeds the density of hexagonal graphene by 7 - 28 %. The structure of the studied diamond-like bilayers contains pores with a maximum diameter of ~4.5 Ă . The calculation of the electronic properties showed that the DL3-12 and DL4â6â12 bilayers should be semiconductors with the direct band gap widths of 1.7 and 2.3 eV, respectively. It is also found that the diamond-like DL3-12 bilayer is stable up to 200 K, whereas the DL4â6â12 bilayer stable up to 210 K. In the region of these temperatures, a slight corrugation of the diamond-like bilayers occurs. Destruction of the bilayers is observed at higher temperatures. The most probable method for producing the DL3-12 and DL4â6â12 bilayers consists in strong uniaxial compression of two graphene layers. The diamond-like DL3-12 bilayer can be formed from L3-12 graphene at pressures exceeding 16.7 GPa, while the DL4â6â12 bilayer can be formed from L4â6â12 graphene at 8.6 GPa.