Force Field Parameterization of Actinyl Molecular Cations Using the 12-6-4 Model.

Area of Science:

• Computational Chemistry
• Materials Science
• Nuclear Chemistry

Background:

• Classical molecular dynamics (MD) simulations require accurate force fields (FFs) for actinyl molecular cations (AnO2n+).
• Existing 12-6 FFs for actinyls have limitations in reproducing solvation and thermodynamic properties.
• Actinide migration and extraction processes involve carbonato actinyl species, necessitating reliable simulation models.

Purpose of the Study:

• To develop and validate a new set of 12-6-4 force field parameters for actinyl molecular cations (AnO2n+, n=1,2) from uranium to plutonium.
• To incorporate an induced dipole term (C4) into the non-bonded potential to enhance accuracy.
• To assess the transferability of the developed FFs for simulating carbonato actinyl species.

Main Methods:

• Development of 12-6-4 FFs parameters for actinyl cations using a parametrization method extended from metallic cations.
• Inclusion of an induced dipole term (C4) in the non-bonded potential.
• Classical molecular dynamics (MD) simulations were performed using four water models (TIP3P, SPC/E, OPC3, TIP4Pew).
• Validation through simulation of carbonato actinyl species and comparison of computed EXAFS signals with experimental data.

Main Results:

• The new 12-6-4 FFs with the C4 term accurately reproduce solvation and thermodynamic properties of actinyl cations.
• MD simulations of carbonato actinyl species showed good agreement with experimental EXAFS signals, demonstrating FF transferability.
• The developed FFs offer improved performance compared to classic 12-6 potentials for actinyl cations.

Conclusions:

• The developed 12-6-4 FFs with induced dipole terms provide a significant advancement for simulating actinyl cations.
• These FFs enhance the accuracy of molecular dynamics simulations for actinide chemistry, including migration and extraction.
• The study opens new avenues for computational research in actinide chemistry and related environmental applications.