Aqueous Fe2S2 cluster: structure, magnetic coupling, and hydration behaviour from Hubbard U density functional theory

Area of Science:

• Computational chemistry
• Materials science
• Inorganic chemistry

Background:

• The Fe2S2 cluster is a fundamental unit in various chemical and biological systems.
• Accurate theoretical modeling of such clusters in solution is crucial for understanding their properties.

Purpose of the Study:

• To investigate the electronic structure and properties of the all-ferrous Fe2S2 cluster in aqueous solution using DFT+U.
• To validate the DFT+U approach by comparing gas-phase results with high-accuracy CCSD(T) calculations.

Main Methods:

• Density Functional Theory with on-site Coulomb interaction (DFT+U) calculations.
• Geometry optimization and molecular dynamics simulations.
• Comparison with coupled-cluster calculations (CCSD(T)) and experimental data (X-ray diffraction, Mössbauer spectroscopy).

Main Results:

• An optimized U value was determined by matching gas-phase cluster geometry to CCSD(T) results.
• DFT+U accurately reproduced the experimental geometry and magnetic coupling of the aqueous Fe2S2 cluster.
• Molecular dynamics simulations confirmed the stability of Fe2S2(aq) in water.
• Significant differences in geometry, hydration, and exchange constants were observed between solvated and gas-phase clusters.

Conclusions:

• The DFT+U method, with a carefully chosen U value, provides a reliable description of the Fe2S2 cluster in aqueous solution.
• The aqueous Fe2S2 cluster exhibits distinct structural and dynamic properties compared to its gas-phase counterpart.
• This study highlights the importance of including solvation effects for accurate modeling of iron-sulfur clusters.