High-Pressure Polymeric Nitrogen Allotrope with the Black Phosphorus Structure

At a Glance

Metadata	Details
Publication Date	2020-05-28
Journal	Physical Review Letters
Authors	Dominique Laniel, B. Winkler, Timofey Fedotenko, Anna Pakhomova, Stella Chariton
Institutions	Deutsches Elektronen-Synchrotron DESY, Dassault Systèmes (United Kingdom)
Citations	176
Analysis	Full AI Review Included

Technical Analysis and Material Solutions for Extreme Condition Research

Documentation Generated for 6CCVD.com

This analysis summarizes the findings of the research paper, “High-pressure polymeric nitrogen allotrope with the black phosphorus structure,” focusing specifically on the material requirements and technical challenges addressed by 6CCVD’s advanced MPCVD diamond capabilities.

Executive Summary

The synthesis and structural characterization of the novel polymeric nitrogen allotrope (bp-N) represent a significant achievement in high-pressure physics and materials science. This work is fundamentally dependent on the extreme performance of the diamond anvil cell (DAC) platform.

Core Achievement: Unambiguous synthesis and identification of bp-N, a polymeric nitrogen allotrope isostructural to black phosphorus, resolving previous discrepancies regarding the LP-N phase.
Extreme Conditions: Synthesis was achieved at ultra-high pressures (140 GPa) and temperatures (up to ~4000 K) within a BX90-type Diamond Anvil Cell (DAC).
Material Properties: bp-N is identified as a wide bandgap semiconductor (2.2 eV at 150 GPa), making it a high-energy density material (HEDM) with unique electronic properties.
Structural Confirmation: In situ synchrotron single-crystal X-ray diffraction (XRD) combined with Raman spectroscopy and Density Functional Theory (DFT) calculations were essential for structural verification (Space Group Cmce).
Diamond Necessity: The successful execution of this experiment—especially the laser heating and subsequent complex characterization—requires defect-free, optically pure, and precisely cut Single Crystal Diamond (SCD) anvils capable of extreme compression.
6CCVD Relevance: This research exemplifies the need for custom, ultra-high quality SCD for advanced HPHT (High-Pressure/High-Temperature) crystallography and novel material synthesis.

Technical Specifications

The following hard data points were extracted, detailing the experimental parameters and resulting material properties of the bp-N phase:

Parameter	Value	Unit	Context / Source
Synthesis Pressure	140	GPa	Required pressure for bp-N formation
Synthesis Temperature	~4000	K	Peak laser heating temperature
Diamond Culet Diameter	80	µm	Size of the SCD anvils used in the DAC
Sample Cavity Diameter	40	µm	Size of laser-drilled cavity in Rhenium gasket
Initial Gas Loading Pressure	~1200	bar	Starting pressure of pure nitrogen gas
Resulting Space Group	Cmce	-	Orthorhombic structure of bp-N
Volume per N atom (Exp., 140 GPa)	39.88(6)	Å³	Unit cell volume measurement
Energy Bandgap	2.2	eV	Wide bandgap calculated at 150 GPa
Shortest Interlayer Distance	2.329(6)	Å	N-N distance between layered strata (140 GPa)
Shortest Intralayer Bond Length (ZZ)	1.338(6)	Å	Shortest N-N bond in the zigzag chain (140 GPa)
Highest Raman Mode Frequency	1308	cm^-1	Intense vibrational mode measured at 140 GPa

Key Methodologies

The experiment successfully synthesized the bp-N allotrope using a meticulous high-pressure, high-temperature procedure that relied entirely on the integrity and optical properties of the MPCVD diamond anvils:

DAC Preparation: A BX90-type diamond anvil cell was prepared with 80 µm diameter SCD culets.
Gasket Fabrication: A 200 µm thick Rhenium (Re) foil was indented down to 12 µm, and a 40 µm diameter sample cavity was laser-drilled.
Loading: The cavity was loaded with pure nitrogen gas (~1200 bars) and submicron-sized Gold (Au) particles (~2 µm) serving as both YAG laser absorbers and internal pressure gauges.
Compression and Initial Heating: The sample was compressed to 124 GPa and laser-heated to 2600 K. Weak diffraction spots appeared, but could not be indexed to known phases.
Reheating and Conversion: Pressure was increased to 140 GPa and the sample was reheated to ~4000 K, promoting further solid conversion into the new bp-N phase.
Characterization: Synchrotron single-crystal X-ray diffraction was performed in situ on the polycrystalline sample, followed by Raman spectroscopy measurements, confirming the bp-N structure.
Decompression: The sample was characterized during decompression down to 86 GPa.

6CCVD Solutions & Capabilities

This research highlights the absolute necessity of high-grade, precisely manufactured Single Crystal Diamond (SCD) for pioneering research at extreme conditions. 6CCVD is an expert provider of SCD platforms specifically engineered for High-Pressure/High-Temperature (HPHT) applications, such as the Diamond Anvil Cell utilized in this study.

Applicable Materials

To replicate or advance the fundamental physics investigated in this paper (ultra-HPHT crystallography and synthesis of HEDMs), the following 6CCVD materials are essential:

Material Grade	Application in HPHT Research	6CCVD Capability Highlight
Optical Grade Single Crystal Diamond (SCD)	Anvils for DACs, optical windows for synchrotron beamlines, laser heating platforms. SCD ensures minimal structural defects (e.g., Type IIa purity) critical for handling pressures >140 GPa and transmitting high-power laser energy (~4000 K).	We supply SCD plates up to 500 µm thick, optimized for low absorption and high thermal conductivity required in laser-heated DACs.
High-Purity Polycrystalline Diamond (PCD)	Gaskets, support rings, or structural components surrounding the anvil. Our inch-size PCD material provides exceptional thermal management and mechanical support.	PCD wafers available up to 125mm in diameter, suitable for large-scale structural support or specialized high-volume applications.
Boron-Doped Diamond (BDD)	Replication experiments involving in situ electronic measurements. The discovery of bp-N as a semiconductor (2.2 eV) suggests BDD could be used as high-pressure electrodes to study conductivity or measure the bandgap shift under pressure.	6CCVD offers heavy Boron-Doped Diamond customizable for resistivity, ideal for conductive DAC electrodes.

Customization Potential for Extreme Condition Engineers

The use of specific dimensions (80 µm culets, 40 µm sample cavity) and metallic components (Rhenium gasket, Gold absorber/gauge) requires specialized diamond processing capabilities that 6CCVD provides:

Precision Processing: We offer custom diamond wafers and plates cut to exact dimensions, capable of being shaped into specific geometries required for DAC culets (e.g., 80 µm diameter).
Ultra-low Roughness Polishing: Achieving reliable optical transparency and stress distribution in anvils requires pristine surfaces. 6CCVD guarantees surface roughness (Ra) less than 1 nm for SCD, which is crucial for maximizing laser transmission and minimizing thermal runaway during 4000 K heating experiments.
Custom Metalization & Patterning: The experiment used Au as a laser absorber and gauge. 6CCVD offers in-house metalization services, including Ti, W, Cu, Pt, Pd, and Au, allowing researchers to pattern thin-film heaters, pressure contacts, or integrated gauge materials directly onto the SCD anvils or specialized micro-gaskets.
Global Logistics: We provide reliable global shipping options (DDU default, DDP available) to ensure rapid delivery of critical, high-value diamond components to synchrotron and HPHT labs worldwide (like DESY, APS, and others listed in the paper’s affiliations).

Engineering Support

The successful synthesis of novel polymeric phases like bp-N requires deep collaboration between materials suppliers and experimental physicists. 6CCVD’s in-house PhD team specializes in diamond material science and can assist researchers facing similar challenges in:

Material Selection: Determining the optimal SCD crystal orientation, purity (Type IIa), and thickness required for specific pressure thresholds (up to and beyond the 140 GPa achieved here).
HPHT Project Design: Consulting on material specifications for HEDM synthesis projects, particularly those involving complex in situ characterization methods like synchrotron XRD and high-fidelity Raman spectroscopy.

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

View Original Abstract

Studies of polynitrogen phases are of great interest for fundamental science and for the design of novel high energy density materials. Laser heating of pure nitrogen at 140 GPa in a diamond anvil cell led to the synthesis of a polymeric nitrogen allotrope with the black phosphorus structure, bp-N. The structure was identified in situ using synchrotron single-crystal x-ray diffraction and further studied by Raman spectroscopy and density functional theory calculations. The discovery of bp-N brings nitrogen in line with heavier pnictogen elements, resolves incongruities regarding polymeric nitrogen phases and provides insights into polynitrogen arrangements at extreme densities.

Tech Support

Original Source

DOI: https://doi.org/10.1103/physrevlett.124.216001

References

2006 - Polymeric Nitrogen: The Ultimate, Green High Performing Energetic Material