Chemical Bonding between Helium and Fluorine under Pressure.

Area of Science:

• Materials Science
• Quantum Chemistry
• High-Pressure Physics

Background:

• Helium-bearing compounds are of interest for their unique structures and properties.
• Helium's inert nature and energetics have prevented helium bond formation previously.

Purpose of the Study:

• To investigate the possibility of forming helium bonds under high pressure.
• To characterize the structure and bonding of novel helium compounds.

Main Methods:

• Ab initio evolutionary structure search to predict stable phases.
• Electronic structure calculations including electronic localization function, crystal orbital Hamilton population, electron density topological analysis, and Bader charge analysis.
• Molecular orbital calculations to analyze bonding interactions.

Main Results:

• A stable compound, He3F2, was discovered at multi-TPa pressures.
• He3F2 features F-shared HeF2 herringbone chains.
• Helium's 1s electrons participate in bonding, forming polar covalent He-F bonds, challenging helium's inertness.

Conclusions:

• The formation of polar covalent He-F bonds in He3F2 under high pressure is demonstrated.
• This discovery expands the understanding of chemical bonding and helium's reactivity under extreme conditions.