Weak antiferromagnetic coupling in molecular ring is predicted correctly by density functional theory plus Hubbard U

Area of Science:

• Computational chemistry
• Materials science
• Quantum physics

Background:

• Density Functional Theory (DFT) with the Hubbard U parameter (DFT+U) is widely used for magnetic materials.
• Previous DFT+U studies often lack precise calibration of U parameters for both metal and ligand atoms.
• Understanding spin behavior in manganese-based molecular magnets is crucial for developing new magnetic materials.

Purpose of the Study:

• To calibrate DFT+U parameters for Mn-based molecular magnets using benchmark complexes.
• To investigate the spin density distribution and polarization in manganese complexes with acetate ligands.
• To accurately predict the magnetic properties of Mn(12) molecular wheels.

Main Methods:

• Density Functional Theory with empirical Hubbard U parameter (DFT+U) calculations.
• Calibration of U parameters using five binuclear manganese complexes.
• Application of the calibrated DFT+U method to Mn(12) molecular wheel.

Main Results:

• Calibrated U parameters for both metal and ligand atoms were determined.
• Observed spin density delocalization onto acetate ligands due to pi-back bonding.
• Predicted antiparallel spin alignment in Mn(12) molecular wheel fragments, matching experimental data.
• Optimized ground spin state geometry is critical for accurate predictions.

Conclusions:

• The calibrated DFT+U protocol provides accurate predictions for manganese molecular magnets.
• Spin delocalization onto ligands can alter magnetic interactions, impacting model performance.
• This methodology is valuable for designing single molecule magnets for spintronics and quantum computing.