Samarium: from a distorted-fcc phase to melting under dynamic compression using in-situ x-ray diffraction.

Area of Science:

• Condensed Matter Physics
• Materials Science
• High-Pressure Physics

Background:

• Understanding the behavior of f-electron systems in lanthanides is critical for developing accurate equations of state.
• First-principles calculations like density functional theory (DFT) face challenges with f-electron interactions, necessitating precise experimental data.
• Previous studies on shocked samarium (Sm) reported melting points that lacked direct experimental validation under shock conditions.

Purpose of the Study:

• To experimentally determine the phase transitions and melting behavior of samarium (Sm) under shock compression.
• To provide in-situ X-ray diffraction and temperature measurements along the Hugoniot of samarium.
• To generate high-quality experimental data for constraining theoretical models and equations of state for lanthanides.

Main Methods:

• In-situ X-ray diffraction measurements of shocked samarium (Sm).
• Simultaneous measurement of temperature along the Hugoniot.
• Analysis of diffraction patterns to identify phase transitions and melting points.

Main Results:

• Direct experimental evidence of a distorted face-centered cubic (dfcc) phase in shocked samarium at 23 GPa.
• Observation of melting initiation from the dfcc phase at 33 GPa (1333 K) and complete melting at 40 GPa (1468 K).
• Significant discrepancy with previous shock melt estimations, highlighting the importance of in-situ X-ray measurements.

Conclusions:

• The study provides the first direct experimental evidence of phase transitions and melting points for shocked samarium.
• The obtained data offer critical benchmarks for validating and improving first-principles calculations and equation of state models for lanthanides.
• Discrepancies with prior studies emphasize the necessity of advanced experimental techniques for accurate high-pressure material characterization.