Thermally triggered phononic gaps in liquids at THz scale

At a Glance

Metadata	Details
Publication Date	2016-01-14
Journal	Scientific Reports
Authors	Dima Bolmatov, Mikhail Zhernenkov, D. V. Zav’yalov, Stanislav Stoupin, Alessandro Cunsolo
Institutions	Volgograd State Technical University, Argonne National Laboratory
Citations	39
Analysis	Full AI Review Included

6CCVD Technical Analysis & Product Integration: Thermally Triggered Phononic Gaps in Liquids at THz Scale

Executive Summary

This document analyzes a key research paper utilizing high-quality diamond in extreme environments to probe fundamental acoustic phenomena, directly linking experimental requirements to 6CCVD’s advanced MPCVD Single Crystal Diamond (SCD) and Polycrystalline Diamond (PCD) capabilities.

Core Achievement: Observation and characterization of thermally triggered low-frequency transverse phononic gaps and high-frequency phononic mode localization in monatomic liquid Argon (Ar) at the Terahertz (THz) scale.
Experimental Method: Inelastic X-ray Scattering (IXS) measurements conducted within a high-pressure/high-temperature Diamond Anvil Cell (DAC).
Material Necessity: The integrity and low background scattering of the full diamond anvils were critical to performing sensitive IXS experiments across extreme thermodynamic conditions (up to 1.08 GPa and 438 K).
Fundamental Crossover: The emergence of these phononic gaps is linked to dynamic and structural phase crossovers across the Frenkel Line thermodynamic boundary.
Application Relevance: Findings provide crucial knowledge for engineering and developing next-generation THz thermal devices, phononic metamaterials, phononic lenses, and mirrors, demanding materials with ultra-high thermal and acoustic control, like CVD diamond.
6CCVD Value Proposition: 6CCVD supplies custom, high-purity Optical Grade SCD and precision-engineered diamond components required for robust, low-noise high-pressure optical/acoustic setups.

Technical Specifications

Parameter	Value	Unit	Context
Temperature Range (Experimental)	298 to 438	K	Range spanning rigid liquid to non-rigid fluid phases (across Frenkel Line)
Pressure Range (Experimental)	0.8 to 1.08	GPa	High-pressure, high-temperature conditions
Diamond Anvil Culet Size	500	µm	Dimensions of the full diamond anvils used in the BX90 DAC
IXS Photon Energy	23.724	keV	Energy used for Inelastic X-ray Scattering
IXS Resolution (FWHM)	≈2	meV	Energy resolution of the IXS spectrometer
Spectrometer Q-Resolution	≈2	nm^-1	Momentum transfer resolution
Low-Frequency Transverse Gap (Emergent)	< 2	meV	Low-energy cutoff observed upon heating (T = 438 K)
Thickness of Rhenium Gasket (Pre-indented)	90	µm	Used to contain the ⁴⁰Ar sample
Dynamic Crossover Timescale	1 to 1.5	ps	Characteristic time for the VACF solid-like feature

Key Methodologies

The successful characterization of THz phononic gaps relied on precise control over extreme pressure and temperature conditions, requiring high-stability diamond components and advanced IXS techniques.

High-Pressure Setup: Experiments were conducted using a BX90 Diamond Anvil Cell (DAC) at the Advanced Photon Source (APS). The DAC utilized tungsten-carbide seats and high-quality, full diamond anvils (500 µm culet size).
Sample Preparation: A Rhenium gasket (250 µm initial thickness, pre-indented to 90 µm) was used, hosting a 220 µm diameter sample hole.
Sample Loading and Calibration: Argon (⁴⁰Ar) was loaded via a gas-loading system up to 1.08 GPa. Pressure was monitored using a Ruby sphere internal standard.
Heating and Equilibration: Conventional resistive heating was used to achieve high temperatures. The DAC was thermally stabilized for a minimum of 15 minutes before collecting each IXS spectrum.
IXS Data Collection: Inelastic X-ray Scattering spectra were collected at a photon energy of 23.724 keV. Data interpretation required careful accounting for background scattering originating from the diamond DAC windows.
Simulation Integration: Molecular Dynamics (MD) simulations (using LAMMPS and Lennard-Jones parameters) were performed and convoluted with the measured instrumental resolution functions to accurately model the experimental spectra, particularly compensating for resolution limitations.

6CCVD Solutions & Capabilities

6CCVD provides the specialized CVD diamond components necessary to replicate and extend these complex high-pressure/high-frequency experiments, ensuring minimal background scattering and maximum thermal stability.

Applicable Materials

To achieve the highest fidelity data in IXS experiments—especially where scattering from the DAC windows must be minimized—researchers require ultra-high-purity, low-defect diamond.

Material Recommendation: Optical Grade Single Crystal Diamond (SCD).
- Value Proposition: 6CCVD’s SCD material is grown via MPCVD, offering superior crystal purity, extremely low impurity incorporation, and excellent uniformity, minimizing parasitic scattering and absorption in the THz and X-ray regimes compared to typical industrial-grade diamond.
Thermal Management Integration: For applications focused on the thermal aspect of phononic gaps (THz thermal devices), Boron-Doped Diamond (BDD) thin films can be integrated onto the SCD surface to act as highly uniform, high-stability resistive heating elements within the DAC.

Customization Potential for High-Pressure Physics

The paper utilized standard 500 µm culets, but extreme-condition research often requires specific geometries and material integration that 6CCVD routinely delivers.

Capability	6CCVD Offering	Relevance to THz & DAC Research
Custom Dimensions	Plates/wafers up to 125mm (PCD)	Enables scaling of experiments and production of large-area substrates for phononic metamaterials.
Precision Shaping	Custom dimensions, precise culet sizes, and specific angles via advanced laser cutting services.	Essential for replicating specialized DAC anvils and creating microfluidic/acoustic channel structures in diamond.
Thickness Control	SCD up to 500 µm; Substrates up to 10 mm.	Allows for optimization of the diamond window thickness to balance mechanical strength (pressure containment) and minimizing X-ray path length (reducing background noise).
Surface Finish	Ra < 1 nm (SCD), Ra < 5 nm (PCD).	Critical for high-pressure seals (smooth contact surfaces in DACs) and for high-frequency optical applications (phononic lenses/mirrors).
Custom Metalization	Au, Pt, Pd, Ti, W, Cu capabilities.	Required for integrating electrical contacts or resistive heating circuits directly onto the diamond anvil surfaces, crucial for thermal control (as performed in the referenced study via resistive heating).

Engineering Support & Expertise

The complexity of controlling atomic dynamics at the THz scale requires materials engineered to specific thermal, acoustic, and purity standards.

Target Application Support: 6CCVD’s in-house PhD engineering team specializes in diamond material selection and design for extreme thermal and acoustic applications, including high-frequency sound propagation, THz spectroscopy, and high-pressure experimental apparatus.
Focus Area: We assist researchers and engineers in selecting optimal SCD or PCD grades to minimize phonon scattering losses, enhance thermal conductivity, and ensure robust performance under GPa-scale pressures necessary for next-generation THz thermal devices, phononic lenses, and THz metamaterials.

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

Tech Support

Original Source

DOI: https://doi.org/10.1038/srep19469