Thermodynamic and structural features of aqueous Ce(III)

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Solution Chemistry

Background:

• Lanthanide(III) ions are crucial in various chemical applications.
• Accurate prediction of their hydration properties is essential for understanding their behavior in solution.
• Cerium(III) serves as a simple model for benchmarking computational methods due to its single f-electron.

Purpose of the Study:

• To benchmark density functionals and reaction field models for hydrated Cerium(III) ions.
• To assess the importance of multiconfigurational character in Cerium(III) wave functions.
• To determine the free energy of water exchange between different coordination numbers.

Main Methods:

• Density Functional Theory (DFT) calculations.
• Complete Active Space Self-Consistent Field (CASSCF) calculations.
• Polarized continuum models (UA0, UAKS, Pauling, UFF) for solvation.

Main Results:

• CASSCF confirmed single-configuration wave functions for octa- and nona-aqua Ce(III).
• Different polarized continuum models showed varying performance in predicting hydration energies.
• Results were largely independent of the specific density functional used.
• The free energy for water exchange between coordination numbers 8 and 9 was estimated at approximately -4 kcal/mol.

Conclusions:

• Computational methods can accurately predict thermodynamic and structural properties of hydrated Cerium(III).
• The choice of reaction field model is critical for accurate solvation energy predictions.
• This work provides a benchmark for future studies on lanthanide ion solvation.