[Mg₃@C₂₀]⁺: an s-orbital electron spin system protected in a carbon ring framework

Area of Science:

• Quantum computing materials
• Molecular magnetism
• Computational chemistry

Background:

• Designing molecular qubits requires suppressing unwanted spin couplings.
• Electron spin-based qubits are promising for quantum information processing.
• Rigid ligands and high s-orbital character are key design principles.

Purpose of the Study:

• Investigate the electronic structure and magnetic properties of [Mg3@C20]+.
• Evaluate the potential of this system for electron spin-based molecular qubits.
• Determine the nature of the unpaired electron's spin density.

Main Methods:

• Density Functional Theory (DFT) calculations.
• Complete Active Space Self-Consistent Field (CASSCF) method.
• Analysis of electronic structure and magnetic properties.

Main Results:

• The unpaired electron is localized on the Mg3 cluster with 67% s-orbital character.
• Mg-Mg bonds show significant covalent character.
• Nearly isotropic g-factors and hyperfine coupling parameters were observed.

Conclusions:

• The [Mg3@C20]+ cluster exhibits an s-orbital electron spin system.
• The carbon ring effectively protects the spin state.
• This system serves as a promising model for electron spin-based two-level states in molecular qubits.