Aqueous Solvation of SmI₂: A Born-Oppenheimer Molecular Dynamics Density Functional Theory Cluster Approach

Area of Science:

• Computational Chemistry
• Physical Chemistry
• Materials Science

Background:

• Aqueous solvation of metal ions is crucial for understanding chemical processes.
• Samarium diiodide (SmI2) is an inorganic compound with interesting properties.

Purpose of the Study:

• To investigate the aqueous solvation structure of SmI2 using molecular dynamics simulations.
• To determine the coordination number and solvation shell structure of Sm(II) in water.
• To compare simulation results with experimental data for similar ions.

Main Methods:

• Born-Oppenheimer molecular dynamics (BOMD) simulations.
• Cluster microsolvation approach with 32 water molecules.
• M062X functional and 6-31G** basis sets for electronic structure calculations.
• Stuttgart-Köln relativistic effective-core potentials for Sm and I atoms.

Main Results:

• SmI2 in water shows swift substitution of iodide ions by water molecules around Sm(II).
• A rigid first solvation shell of 8.4 water molecules is predicted (2.6–3.4 Å).
• A second solvation sphere is observed from 3.5 to 6 Å.
• The Sm(II)-O radial distribution function agrees well with experimental data for Sr2+.
• No water exchange events were detected around Sm2+ after microsolvation.

Conclusions:

• Sm(II) exhibits a stable and rigid first solvation shell in aqueous solution.
• The solvation behavior of Sm2+ is comparable to Sr2+ and Eu2+ due to similar ionic radii and charge-to-radius ratios.
• BOMD simulations provide valuable insights into the solvation dynamics of SmI2.