Shared and closed-shell O-O interactions in silicates

Area of Science:

• Solid-state chemistry
• Materials science
• Computational chemistry

Background:

• Silicates commonly exhibit O-O bond paths between coordination polyhedra.
• These bond paths are characterized by maximum electron density and weak closed-shell interactions.

Purpose of the Study:

• To investigate the nature and origin of O-O bond paths in silicates.
• To differentiate between closed-shell and shared interactions based on electron density properties.

Main Methods:

• Analysis of electron density, rho(rc), and local electronic energy density, H(rc), at bond critical points, rc.
• Modeling based on O-O separation, R(O-O), and distances of Si atoms from the midpoint.
• Comparison with M-O bonded interactions for various metal atoms (M).

Main Results:

• O-O bond paths in coesite were partitioned into domains with and without these paths.
• Weak closed-shell O-O interactions show increasing H(rc) with increasing rho(rc), similar to closed-shell M-O interactions.
• The O2 molecule in silica III exhibits a shared interaction, evidenced by negative H(rc).

Conclusions:

• O-O bond paths can arise from metal atom electron density superposition or contribute to structural stabilization.
• Electron density properties, specifically H(rc), effectively distinguish between closed-shell and shared interactions.
• The findings provide insights into bonding mechanisms in silicate structures.