Advancing neutron diffraction for accurate structural measurement of light elements at megabar pressures

Area of Science:

• High-pressure science
• Materials science
• Condensed matter physics
• Neutron scattering

Background:

• The diamond anvil cell (DAC) is a primary tool for high-pressure research, enabling megabar pressure studies with X-ray and spectroscopy.
• Neutron diffraction has been limited to lower pressures due to low neutron flux and large sample size requirements.

Purpose of the Study:

• To introduce a novel neutron diamond anvil cell (DAC) capable of extending the accessible pressure range for neutron diffraction.
• To overcome the limitations of previous neutron diffraction techniques in high-pressure environments.

Main Methods:

• Development of a neutron DAC incorporating ball-bearing guides for enhanced mechanical stability.
• Utilized gem-quality synthetic diamonds with novel anvil support and improved in-seat collimation.
• Performed neutron diffraction experiments at extreme pressures.

Main Results:

• Achieved a record pressure of 1.15 megabars (Mbar).
• Successfully conducted crystallographic analysis at 1 Mbar using nickel as a model material.
• Investigated the phase behavior of graphite up to 0.5 Mbar.

Conclusions:

• The developed neutron DAC significantly expands the pressure range for neutron diffraction studies.
• Enables structural characterization of materials, particularly low-Z elements, which are challenging for X-ray methods.
• Represents a significant advancement for high-pressure materials science research.