Ions in solutions: Determining their polarizabilities from first-principles

Area of Science:

• Computational chemistry
• Quantum mechanics
• Materials science

Background:

• Accurate modeling of ion behavior in aqueous solutions is crucial for understanding chemical processes.
• Polarizability, a key electronic property, influences interatomic and intermolecular interactions.
• First-principles calculations offer a rigorous approach to determining these properties.

Purpose of the Study:

• To compute the dipole polarizabilities of various ions in aqueous solutions.
• To investigate the influence of the aqueous environment on ion polarizabilities compared to gas-phase values.
• To provide data for developing improved interaction potentials that include polarization effects.

Main Methods:

• Utilizing density functional theory (DFT) to study the linear response of maximally localized Wannier functions to an external electric field.
• Employing ab initio molecular dynamics simulations for dynamic systems like H(+) and OH(-).
• Calculating the polarizability tensor for anisotropic molecular ions.

Main Results:

• Most monoatomic cations (e.g., Li(+), Na(+), Ca(2+)) show gas-phase polarizabilities in solution.
• Anions (F(-), Cl(-), Br(-), I(-)) and Cs(+) exhibit reduced polarizabilities in water due to environmental effects.
• Dynamic polarizability changes were observed during proton transfer events for H(aq)(+) and OH(aq)(-).
• The polarizability tensor was computed for the uranyl ion (UO(2)(2+)).

Conclusions:

• Aqueous environments significantly affect the polarizability of certain ions, particularly anions.
• The computed polarizabilities are essential for accurate simulations and the development of refined interaction potentials.
• This work provides valuable insights into the electronic response of ions in solution.