Predicted Formation of H3(+) in Solid Halogen Polyhydrides at High Pressures

Area of Science:

• Condensed matter physics
• Computational chemistry
• Materials science

Background:

• Halogen polyhydrides (HnX) are compounds of hydrogen and halogens.
• Understanding their behavior under extreme pressure is crucial for materials science.

Purpose of the Study:

• To investigate the structural evolution of compressed halogen polyhydrides (HnX) under high pressure.
• To identify novel stable stoichiometries and phases.

Main Methods:

• Ab initio calculations based on density functional theory (DFT).
• Analysis of structural, electronic, and bonding properties as a function of pressure.

Main Results:

• HnF (n > 1) remain metastable up to 300 GPa.
• Four new stable stoichiometries for HnCl (n > 1) predicted at high pressures: H2Cl, H3Cl, H5Cl, and H7Cl.
• Unexpected triangular H3(+) species observed in H2F, H3F, H5F, and H5Cl above 100 GPa.

Conclusions:

• The formation of H3(+) species is driven by pressure-induced charge transfer from hydrogen to halogen atoms.
• These findings expand the known phase diagrams of halogen polyhydrides under extreme conditions.