Simple Molecules under High‐Pressure and High‐Temperature Conditions - Synthesis and Characterization of α‐ and β‐C(NH)2 with Fully sp3‐Hybridized Carbon
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2023-12-15 |
| Journal | Angewandte Chemie |
| Authors | Thaddäus J. Koller, Siyu Jin, Viktoria Krol, Sebastian J. Ambach, Umbertoluca Ranieri |
| Institutions | Deutsches Elektronen-Synchrotron DESY, China University of Geosciences |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: High-Pressure Carbon Nitride Synthesis
Section titled “Technical Documentation & Analysis: High-Pressure Carbon Nitride Synthesis”Executive Summary
Section titled “Executive Summary”This research details the successful synthesis and characterization of two novel, fully sp³-hybridized carbon diimide phases, $\alpha$-C(NH)₂ and $\beta$-C(NH)₂, under extreme High-Pressure/High-Temperature (HPHT) conditions.
- Novel Material Synthesis: Two previously unknown carbon diimide phases, $\alpha$-C(NH)₂ (distorted $\beta$-cristobalite structure) and $\beta$-C(NH)₂ (interpenetrating diamond-like networks), were synthesized using Laser-Heated Diamond Anvil Cells (LHDAC).
- Extreme Conditions: Experiments reached pressures up to 45 GPa and temperatures up to 2400 K, simulating conditions found in the interiors of ice giants like Uranus and Neptune.
- Diamond-Like Properties: The synthesized materials exhibit high bulk moduli (K₀), notably 148 GPa for $\alpha$-C(NH)₂, confirming their potential as high-energy-density materials with desirable properties like high hardness and thermal conductivity.
- Methodology: The study relied critically on in situ Synchrotron X-ray Diffraction (XRD) and Density Functional Theory (DFT) calculations to determine crystal structures and thermodynamic stability domains.
- Recoverability: $\beta$-C(NH)₂ was found to be fully recoverable and stable at ambient conditions, highlighting its potential for technological applications.
- 6CCVD Relevance: The entire experimental framework depends on the mechanical and optical integrity of high-ppurity Single Crystal Diamond (SCD) anvils, a core product of 6CCVD.
Technical Specifications
Section titled “Technical Specifications”The following hard data points were extracted from the LHDAC experiments and subsequent analysis:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Maximum Experimental Pressure | 45 | GPa | DAC-2 (DCDA starting material) |
| Maximum Experimental Temperature | 2400 | K | DAC-1 (Malononitrile starting material) |
| Bulk Modulus (K₀) - $\alpha$-C(NH)₂ | 148 ± 2 | GPa | Determined via 3rd order BMEOS (Experimental) |
| Bulk Modulus (K₀) - $\beta$-C(NH)₂ | 93 ± 4 | GPa | Determined via 2nd order BMEOS (Experimental) |
| Diamond Bulk Modulus (Reference) | 446 | GPa | Benchmark for HPHT materials |
| $\alpha$-C(NH)₂ Lattice Parameters | a=5.3617(14), b=5.6277(16), c=6.130(4) | Å | At 37 GPa, Space Group Fdd2 (no. 43) |
| $\beta$-C(NH)₂ Lattice Parameters | a=10.85(4), b=11.391(12), c=12.396(11) | Å | At 36 GPa, Space Group Fddd (no. 70) |
| C-N Bond Length Range ($\alpha$-C(NH)₂) | 1.421 to 1.435 | Å | Indicative of single covalent bonds |
| N-C-N Bond Angle ($\alpha$-C(NH)₂) | 120.06 ± 0.11 | ° | Suggests sp2 hybridization of Nitrogen |
| $\beta$-C(NH)₂ Stability | Fully Recoverable | N/A | Stable to ambient conditions and in air |
Key Methodologies
Section titled “Key Methodologies”The synthesis and characterization of the novel carbon nitrides relied on precise control of extreme conditions using specialized diamond equipment and advanced synchrotron techniques.
- High-Pressure Setup: BX90-type Diamond Anvil Cells (DACs) were used to compress starting materials (malononitrile, dicyandiamide (DCDA), and melamine) to target pressures between 36 GPa and 45 GPa.
- Laser Heating (LHDAC): Samples were heated using a laser, with power increased stepwise until an intense flash of light was observed, sustained for approximately five seconds. Temperatures exceeding 1000 K were measured prior to the flash, with maximum temperatures reaching 2400 K.
- In Situ X-ray Diffraction (XRD): Product analysis was performed in situ using Synchrotron XRD at the Extreme Conditions Beamline P02.2 (DESY) and the High Pressure Beamline ID27 (ESRF).
- Structural Determination: Single-Crystal X-ray Diffraction (SCXRD) was crucial for resolving the crystal structures of the previously unknown $\alpha$-C(NH)₂ and $\beta$-C(NH)₂ phases.
- Compressibility Analysis: Stepwise decompression was performed to collect SCXRD data, allowing for the determination of the Bulk Modulus (K₀) and stability domains using the Birch-Murnaghan Equation of State (BMEOS).
- Theoretical Modeling: Density Functional Theory (DFT) calculations were employed to verify experimental K₀ values, predict hydrogen atom positions, and compare the relative thermodynamic stabilities ($\Delta$H and $\Delta$G) of the observed phases across different pressures and temperatures.
6CCVD Solutions & Capabilities
Section titled “6CCVD Solutions & Capabilities”The successful execution of this HPHT research hinges on the quality and reliability of the diamond anvils used in the LHDAC setup. 6CCVD specializes in providing the high-purity, low-defect MPCVD diamond required for such demanding applications.
| Research Requirement | 6CCVD Solution & Capability | Technical Advantage |
|---|---|---|
| High-Pressure Anvils (45 GPa) | Optical Grade Single Crystal Diamond (SCD) | SCD offers the highest mechanical strength and bulk modulus (446 GPa), ensuring maximum pressure containment and anvil longevity in extreme environments. |
| Laser Heating Transparency (LHDAC) | Low-Defect, Type IIa SCD Material | Our MPCVD SCD is grown with extremely low nitrogen content, minimizing absorption of the heating laser and ensuring high optical clarity for both heating and observation windows. |
| Synchrotron Beam Transmission | Precision Polishing (Ra < 1 nm) | SCD plates are polished to an atomic finish (Ra < 1 nm), minimizing X-ray scattering and maximizing the signal-to-noise ratio for critical in situ SCXRD measurements. |
| Custom DAC Geometry | Custom Dimensions & Laser Cutting | We provide custom-cut SCD plates and wafers (up to 500 µm thick) tailored to specific DAC designs (e.g., BX90, toroidal, or specialized LHDAC configurations). |
| Electrical Measurement Integration | Internal Metalization Services | For future HPHT experiments requiring electrical monitoring (e.g., resistance changes during synthesis), 6CCVD offers custom metalization (Au, Pt, Ti, W, Cu) directly onto the diamond surface. |
Applicable Materials
Section titled “Applicable Materials”To replicate or extend this high-pressure synthesis research, the following 6CCVD materials are recommended:
- Optical Grade SCD: Essential for the diamond anvils, providing the necessary mechanical robustness, thermal stability, and optical transparency for LHDAC and synchrotron analysis.
- High-Purity SCD Substrates: Available in thicknesses from 0.1 µm up to 500 µm, allowing researchers to select the optimal geometry for pressure generation and optical access.
Customization Potential
Section titled “Customization Potential”The complexity of HPHT research often requires non-standard components. 6CCVD supports the engineering community by offering:
- Custom Dimensions: Plates/wafers up to 125 mm (PCD) and custom SCD sizes for specialized DACs.
- Precise Thickness Control: SCD thickness can be controlled from 0.1 µm to 500 µm, crucial for optimizing the working distance and pressure profile of the anvil.
- Advanced Polishing: We offer ultra-smooth polishing (Ra < 1 nm for SCD) to ensure maximum optical performance and minimal beam interference.
Engineering Support
Section titled “Engineering Support”6CCVD’s in-house PhD team, comprised of expert material scientists, can assist with material selection and design optimization for similar High-Pressure/High-Temperature Synthesis projects, ensuring that the diamond components meet the stringent demands of extreme condition research.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract The elements hydrogen, carbon, and nitrogen are among the most abundant in the solar system. Still, little is known about the ternary compounds these elements can form under the high‐pressure and high‐temperature conditions found in the outer planets’ interiors. These materials are also of significant research interest since they are predicted to feature many desirable properties such as high thermal conductivity and hardness due to strong covalent bonding networks. In this study, the high‐pressure high‐temperature reaction behavior of malononitrile H 2 C(CN) 2 , dicyandiamide (H 2 N) 2 C=NCN, and melamine (C 3 N 3 )(NH 2 ) 3 was investigated in laser‐heated diamond anvil cells. Two previously unknown compounds, namely α‐C(NH) 2 and β‐C(NH) 2 , have been synthesized and found to have fully sp 3 ‐hybridized carbon atoms. α‐C(NH) 2 crystallizes in a distorted β‐cristobalite structure, while β‐C(NH) 2 is built from previously unknown imide‐bridged 2,4,6,8,9,10‐hexaazaadamantane units, which form two independent interpenetrating diamond‐like networks. Their stability domains and compressibility were studied, for which supporting density functional theory calculations were performed.