A DFT investigation of the electronic, optical, and thermoelectric properties of pentadiamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-11-21 |
| Journal | Chemical Physics Letters |
| Authors | Raphael M. Tromer, Levi C. Felix, Cristiano F. Woellner, Douglas S. GalvĂŁo |
| Institutions | Universidade Federal do ParanĂĄ, Universidade Estadual de Campinas (UNICAMP) |
| Citations | 45 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive Summaryâ- Material Focus: Pentadiamond, a novel 3D carbon allotrope characterized by mixed sp2 and sp3-like hybridization.
- Electronic Properties: It is an indirect bandgap semiconductor. The calculated bandgap is 3.31 eV (using the high-accuracy HSE06 functional), positioning it as a wide-bandgap material.
- Optical Activity: Pentadiamond exhibits strong optical activity exclusively in the Ultra-Violet (UV) range, remaining transparent in the infrared and visible spectrums.
- Reflectivity Advantage: It demonstrates remarkably low reflectivity, peaking at approximately 40% at 17 eV across the optical spectrum. This is significantly lower than diamond (70%) and 8-tetra(2,2) (60%) in the high-energy UV region.
- Key Application: Due to its low reflectivity and strong UV absorption, pentadiamond is proposed as a highly efficient material for use as a UV collector or detector, particularly effective for photon energies up to 15 eV.
- Static Constants: The material possesses a static dielectric constant of 4.70 and a static refractive index of 2.16.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Bandgap (Indirect) | 3.31 | eV | HSE06 functional corrected value. |
| Bandgap (GGA-PBE) | 2.50 | eV | Calculated using GGA-PBE functional. |
| Static Dielectric Constant (Δ1(0)) | 4.70 | Dimensionless | Pentadiamond (compared to Diamond: 5.40). |
| Static Refractive Index (η(0)) | 2.16 | Dimensionless | Pentadiamond (compared to Diamond: 2.33). |
| Average C-C Bond Length | 1.51 | A | Optimized pentadiamond structure. |
| Density | 2.20 | g/cm3 | Optimized structure (Diamond: 3.54 g/cm3). |
| Atoms per Unit Cell | 22 | Atoms | Pentadiamond primitive supercell. |
| Crystal Structure | FCC (Fm3m, 225) | N/A | Fully isotropic structure. |
| Maximum Absorption Intensity | 2.3 x 106 | cm-1 | Occurs in the UV range (14.0 eV and 16.8 eV). |
| Maximum Reflectivity (R) | ~40% | % | Occurs at 17 eV (low reflectivity across spectrum). |
| UV Collector Range | Up to 15 | eV | Range where low reflectivity makes it superior to diamond. |
Key Methodologies
Section titled âKey Methodologiesâ- First-Principles Calculation: All calculations were performed using Density Functional Theory (DFT) methods, primarily utilizing the SIESTA software package.
- Functional Selection: The Generalized Gradient Approximation (GGA) with the Perdew-Burke-Ernzerhof (PBE) functional was used for the exchange-correlation part.
- Structural Optimization: Geometrical optimizations for pentadiamond, diamond, and 8-tetra(2,2) were carried out using the conjugate gradient method, allowing full relaxation of both atomic positions and lattice vectors.
- Convergence Criteria: Forces on each atom were required to be smaller than 0.005 eV/A.
- Bandgap Correction (HSE06): To overcome the known underestimation of bandgaps by GGA-PBE, a more robust bandgap value was obtained using the HSE06 functional via the Gaussian16 software package (with cc-pVTZ basis set).
- Scissor Operator Application: The corrected bandgap value (EgapHSE06) was used to define a scissor operator (Equation 7) within SIESTA. This operator shifts the unoccupied states, ensuring the optical calculations maintain the accuracy equivalent to the HSE06 functional.
- Optical Analysis: Optical quantities (complex dielectric function, absorption coefficient, reflectivity, refractive index) were calculated in the linear regime. The external electrical field was polarized as an average across the x, y, and z spatial directions.
- Brillouin Zone Sampling: A mesh cutoff energy of 300 Ry and a 10 x 10 x 10 k-point set (Monkhorst-Pack scheme) were used for sampling.
Commercial Applications
Section titled âCommercial ApplicationsâThe unique electronic structure (wide bandgap) and optical properties (low reflectivity, strong UV absorption) of pentadiamond suggest applications in advanced optoelectronics and sensing:
- UV Photodetectors and Sensors: The strong, selective absorption in the UV range (starting near 3.5 eV) makes pentadiamond an ideal active material for high-sensitivity, solar-blind UV detectors.
- High-Efficiency UV Collectors/Harvesters: Its exceptionally low reflectivity (less than 40% up to 17 eV) minimizes light loss, enabling the design of highly efficient UV energy harvesting devices or protective coatings.
- Wide-Bandgap Semiconductor Devices: The 3.31 eV bandgap places it in the class of materials suitable for high-power, high-frequency, and high-temperature electronic components, potentially competing with materials like SiC or GaN.
- Protective/Optical Coatings: Given its transparency in the visible and infrared spectrums, pentadiamond could be used as a transparent coating that selectively absorbs or filters high-energy UV radiation.
Tech Support
Section titled âTech SupportâOriginal Source
Section titled âOriginal SourceâReferences
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