Density Functional Calculations for Aqueous Silver Clusters Containing Water and Nitrate Ligands

Area of Science:

• Computational Chemistry
• Physical Chemistry
• Materials Science

Background:

• Understanding the behavior of ions in aqueous solutions is crucial for various chemical processes.
• Silver-water clusters are relevant in catalysis and solution chemistry.
• The interaction of nitrate ions with metal clusters influences solution properties and reactivity.

Purpose of the Study:

• To investigate the incorporation of nitrate ions into silver-water aqueous clusters.
• To calculate thermodynamic variables and equilibrium constants for nitrate association with silver clusters.
• To explore the structural and electronic properties of these clusters and their implications for silver reduction.

Main Methods:

• Utilized PBE0 density functional theory with the Solvent Model Density (SMD) solvation model.
• Calculated Gibbs free energy of solvation and other thermodynamic variables at 298.15 K.
• Employed cluster-continuum models including solute relaxation and London dispersive forces (D3).

Main Results:

• Calculated free energies of solvation for Ag+ and NO3- agree well with experimental values.
• Equilibrium structures show nitrate oxygen bonding to silver clusters, with water molecules acting as ligands.
• Equilibrium constants for nitrate association with silver clusters were determined, indicating a small ratio of nitrate-containing to nitrate-free clusters.

Conclusions:

• The study provides insights into the structure and stability of silver nitrate clusters in aqueous solution.
• Calculations reveal chain-like structures for Ag(NO3)+ clusters with bidentate oxygen bonds.
• The presence of larger silver clusters favorably influences the reduction potentials of silver clusters in aqueous media.