Selecting Quantum-Chemical Methods for Lanthanide-Containing Molecules: A Balance between Accuracy and Efficiency.

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Lanthanide Chemistry

Background:

• Lanthanide complexes are crucial in various chemical applications.
• Accurate computational modeling of lanthanides is challenging due to their electronic structure.
• Previous studies have used diverse computational methods with varying success.

Purpose of the Study:

• To systematically analyze the impact of different computational methods on lanthanide-containing molecules.
• To identify the most accurate computational approach for predicting properties of lanthanide species.
• To guide future theoretical studies on lanthanides.

Main Methods:

• Density Functional Theory (DFT) with various functionals (B3LYP, TPSSh).
• Basis sets (Sapporo) and relativistic approximations (Douglas-Kroll-Hess - DKH).
• Calculations performed on lanthanide diatomic molecules, larger complexes, and bis(2-ethylhexyl)phosphate structures.

Main Results:

• B3LYP/Sapporo/DKH best reproduced dissociation energies, with a mean absolute deviation of 1.3 kcal/mol compared to CCSDT(Q) calculations.
• TPSSh/Sapporo/DKH showed the smallest deviation for geometries of larger molecular complexes against experimental data.
• TPSSh/Sapporo/DKH accurately predicted separation factors for lanthanide bis(2-ethylhexyl)phosphate structures.

Conclusions:

• The choice of computational method significantly influences the accuracy of calculated lanthanide properties.
• B3LYP/Sapporo/DKH is recommended for accurate dissociation energy calculations.
• TPSSh/Sapporo/DKH is optimal for predicting molecular geometries and separation factors in lanthanide systems.