Probing the subtle differences between promethium and curium

Area of Science:

• Nuclear Chemistry
• Radiochemistry
• Materials Science

Background:

• Curium (Cm) and promethium (Pm) exhibit similar chemical and physical properties, posing significant separation challenges.
• Co-location of processing at Oak Ridge National Laboratory leads to curium contamination in promethium-containing fission product streams.

Purpose of the Study:

• To investigate the fundamental properties of curium and promethium to understand their separation difficulties.
• To computationally and experimentally probe the interactions of these elements within a specific crystal system.

Main Methods:

• Single crystal X-ray diffraction was employed to analyze isostructural compounds.
• Quantum theory of atoms in molecules (QTAIM) was used for computational analysis.
• The study focused on a 2,2 :6 ',2"-terpyridine crystal system.

Main Results:

• Analysis revealed highly similar bonding characteristics between promethium and curium in the studied isostructural compounds.
• Subtle differences in bonding were identified, providing insight into the challenges of separating these elements.
• The study elucidated the fundamental solid-state chemistry of these rare elements.

Conclusions:

• The inherent similarities in bonding, as evidenced by subtle differences, explain the difficulty in separating curium and promethium.
• This research provides experimental data on the solid-state chemistry of promethium and curium.
• The findings reinforce the placement of promethium within the lanthanide series.