Non-thermal structural transformation of diamond driven by x-rays

Area of Science:

• Materials Science
• Condensed Matter Physics
• X-ray Science

Background:

• Intense X-ray free-electron laser (XFEL) pulses can drive non-thermal phase transitions in materials.
• Diamond's unique crystal structure is susceptible to transformations under extreme conditions.

Purpose of the Study:

• To investigate the dynamics of X-ray-induced structural transformation in diamond.
• To determine the dose threshold for graphitization in diamond.

Main Methods:

• Utilized pump-probe XFEL experiments at SACLA to study diamond.
• Analyzed diffraction patterns to track structural changes over time (0-250 fs) and varying X-ray doses (0.9-8.0 eV/atom).
• Performed Debye-Waller analysis and compared experimental data with XTANT+ simulations.

Main Results:

• Observed a decrease in diamond diffraction peak intensities (111, 220, 311) over time, indicating lattice disordering.
• Debye-Waller analysis revealed anisotropic atomic displacements, larger perpendicular to (111) planes.
• Graphitization (002 graphite peak) was confirmed at a 33 ms delay above a 1.2 eV/atom dose threshold.

Conclusions:

• X-ray pulses induce significant non-thermal structural transformation and disordering in diamond.
• Graphitization of diamond occurs above a specific X-ray dose threshold.
• Experimental findings are consistent with hybrid computational models for X-ray-matter interactions.