AA Stacking Phase of Diamane-like Carbon Nitrides - A First Principle Study and Its Thermal Conductivity
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2025-03-19 |
| Journal | ACS Omega |
| Authors | Teerachote Pakornchote, Sakarn Khamkaeo, Annop Ektarawong, Thiti Bovornratanaraks |
| Institutions | Chulalongkorn University, Thailand Center of Excellence in Physics |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive Summaryâ- Novel Material Phase: A new diamane-like carbon nitride phase, AA-NCCN (AA-stacking, P6m2 symmetry), is introduced and computationally analyzed for thermal properties.
- Superior Thermal Conductivity (TC): AA-NCCN exhibits a higher TC (1626 W/mK at 300 K) compared to its AB-stacked counterpart, AB-NCCN (1539 W/mK), and rivals the TC of bulk diamond.
- Symmetry-Driven Enhancement: The enhanced TC is primarily attributed to the Out-of-Plane Acoustic (ZA) phonon mode, whose relaxation time in AA-NCCN is nearly double that in AB-NCCN due to the presence of a horizontal mirror plane.
- Coexistence Potential: DFT calculations show a minimal energy difference (6 meV/atom) between AA-NCCN and AB-NCCN, suggesting they could potentially coexist as stacking faults in synthesized films.
- Phonon Mechanism: The ZA mode is the dominant contributor to thermal transport in AA-NCCN, whereas the Transverse Acoustic (TA) mode dominates in AB-NCCN.
- Methodology: Thermal properties were evaluated using Density Functional Theory (DFT) combined with the Boltzmann Transport Equation (BTE) under the Relaxation Time Approximation (RTA).
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Thermal Conductivity (AA-NCCN) | 1626 | W/mK | At 300 K (RTA/DFT) |
| Thermal Conductivity (AB-NCCN) | 1539 | W/mK | At 300 K (RTA/DFT) |
| Thermal Conductivity (AA-NCCN) | 256 | W/mK | At 1000 K (RTA/DFT) |
| Thermal Conductivity (AB-NCCN) | 239 | W/mK | At 1000 K (RTA/DFT) |
| Energy Difference (AA vs AB) | 6 | meV/atom | AB-NCCN is the lower energy phase |
| In-Plane Lattice Parameter (AA-NCCN) | 2.368 | A | Optimized structure |
| In-Plane Lattice Parameter (AB-NCCN) | 2.392 | A | Optimized structure |
| ZA Mode Relaxation Time Ratio | ~2 | (unitless) | AA-NCCN vs AB-NCCN (at 300 K) |
| Dominant TC Contribution (AA-NCCN) | >35 | % | Out-of-Plane Acoustic (ZA) mode at 300 K |
| Low-Frequency IO Mode (AA-NCCN) | 394.4 | cm-1 | At Gamma (Î) point |
| Low-Frequency ZO Mode (AA-NCCN) | 528.5 | cm-1 | At Gamma (Î) point |
| Plane-Wave Energy Cutoff | 800 | eV | DFT calculations (VASP) |
| Force/Energy Convergence Criteria | 10-6 | eV | Ionic relaxation process |
Key Methodologies
Section titled âKey MethodologiesâThe thermal properties were calculated using a combination of Density Functional Theory (DFT) and the Boltzmann Transport Equation (BTE) under the Relaxation Time Approximation (RTA).
- DFT Setup: Calculations performed using the Vienna ab initio Simulation Package (VASP), employing the Generalized Gradient Approximation (GGA) and the Project Augmented Wave (PAW) method.
- Ionic Relaxation: A Monkhorst-Pack k-point density of 11 x 11 x 1 was used. The plane-wave energy cutoff was set to 800 eV, with convergence criteria of 10-6 eV for both energy and force.
- Interatomic Force Constants (IFCs): Second- and third-order IFCs were calculated using 4 x 4 x 1 supercells for both NCCN phases, implemented via ALAMODE software.
- Displacement Parameters: Atomic displacements were set to 0.01 A for second-order IFCs and 0.04 A for third-order IFCs. A cutoff radius of 4.51 A was applied.
- Vibration Characteristics: Phonon dispersion relations were estimated using second-order IFCs with a q-point density of 20 x 20 x 1.
- Thermal Conductivity Calculation: TC was computed by solving the BTE using the RTA method, requiring third-order IFCs.
- TC Convergence: A high q-point density of 200 x 200 x 1 was utilized to ensure convergence of the relaxation time, heat capacity, and group velocity required for the TC calculation.
Commercial Applications
Section titled âCommercial Applicationsâ- High-Performance Thermal Management: Use in microelectronics and nanoelectronic circuits as an ultrathin heat spreader or sink, leveraging TC comparable to bulk diamond.
- Hard Coating Technology: Application as a superhard material coating, similar to diamane, for industrial tools, protective layers, and high-wear components.
- Advanced 2D Materials Synthesis: Potential precursor material for 2D carbon nitride alloys (e.g., B/N doped diamanes) synthesized under high-pressure conditions (e.g., 10 GPa).
- High-Frequency Devices: Integration into devices requiring materials with high elastic constants and stable thermal properties across a wide temperature range (up to 1000 K).
- Tunable Material Films: Development of films exhibiting coexisting AA- and AB-stacking phases, allowing for fine-tuning of thermal and mechanical properties through controlled stacking fault density.
View Original Abstract
Diamond-derived two-dimensional (2D) materials or diamanes show promising properties such as high elastic constants and giant thermal conductivity. We here present a new phase of diamane variants, AA-NCCN, which is a diamane-like structure of two carbon nitride layers in AA-stacking. Its thermal conductivity is higher than that of AB-NCCN, which is an AB-stacking configuration of NCCN, and hydrogenated diamane, computed by the relaxation time approximation (RTA) method. Because the RTA underestimates the thermal conductivity of some 2D materials, we propose that AA-NCCN could be a candidate whose thermal conductivity rivals that of diamond and a coexisting phase with AB-NCCN.