Hydrogen in actinides: electronic and lattice properties

Area of Science:

• Materials Science
• Solid State Physics
• Quantum Chemistry

Background:

• Actinide hydrides exhibit unique magnetic, electronic, transport, and thermodynamic properties.
• Hydrogen's impact on bonding involves volume expansion and charge transfer, affecting actinide electronic states.

Purpose of the Study:

• To elucidate the general mechanisms of hydrogen's impact on actinide bonding and properties.
• To investigate the magnetic and electronic properties of uranium and plutonium hydrides.
• To explore the potential of actinide polyhydrides for superconductivity.

Main Methods:

• General framework analysis of H impact on bonding.
• Ab-initio computational analyses.
• Spectroscopic studies of sputter-deposited thin films.

Main Results:

• Hydrogenation induces strong magnetism in uranium (UH2, UH3) and plutonium hydrides.
• Magnetic properties arise from 5f-band narrowing, reduced hybridization, and stabilization of specific 5f electronic states.
• Valence-band photoelectron spectra reflect atomic 5f-1 multiplet effects, not directly the 5f ground-state density of states.

Conclusions:

• Hydrogen absorption is a tool for fine-tuning electronic structures near quantum critical points.
• Actinide polyhydrides represent a new frontier with potential for high-temperature superconductivity.