In Situ High-Temperature Raman Spectroscopy of UCl₃: A Combined Experimental and Theoretical Study

Area of Science:

• Nuclear Engineering
• Materials Science
• Spectroscopy

Background:

• Uranium trichloride (UCl3) is crucial for molten salt reactors and nuclear fuel reprocessing.
• Understanding UCl3's thermal properties is vital for reactor safety and efficiency.

Purpose of the Study:

• To experimentally determine the Raman spectra of UCl3.
• To investigate the temperature dependence of UCl3's vibrational modes.
• To compare experimental results with theoretical calculations and other metal chlorides.

Main Methods:

• Experimentally measured Raman spectra of UCl3 from ambient to 871 K.
• Calculated Grüneisen parameter using thermal expansion data and temperature derivatives.
• Performed density functional theory (DFT+U) calculations.

Main Results:

• Observed red-shift in five Raman-active vibrational modes with increasing temperature.
• Determined an average isobaric mode Grüneisen parameter of 0.91 ± 0.02.
• Found good agreement between experimental and DFT+U calculated results.

Conclusions:

• The observed red-shift is attributed to U-Cl bond elongation at higher temperatures.
• The determined Grüneisen parameter provides insights into UCl3's thermal behavior.
• Results provide a foundation for understanding UCl3 in high-temperature nuclear applications.