H2O nucleation around Au+.

Area of Science:

• Computational Chemistry
• Materials Science
• Physical Chemistry

Background:

• Understanding the behavior of metal cation clusters with water is crucial for solvation and nucleation processes.
• Previous studies have explored smaller clusters, but the structural evolution and electronic properties of larger [Au(H2O)n]+ clusters remain less understood.

Purpose of the Study:

• To investigate the ground state geometry, electronic structure, and binding energy of gold cation ([Au(H2O)n]+) clusters.
• To elucidate the structural organization of water molecules around the Au+ ion as a function of cluster size (n=1-10).
• To explore quantum effects in nucleation and charge screening phenomena in these clusters.

Main Methods:

• First principles electronic structure calculations were employed.
• Calculations focused on determining ground state geometries, electronic properties, and binding energies.
• Analysis included structural motifs, coordination shells, and charge distribution.

Main Results:

• The first coordination shell of Au+ consists of two water molecules, forming a stable H2O-Au+-H2O structure.
• Subsequent water molecules aggregate into stable rings, leading to a dumbbell structure at [Au(H2O)8]+.
• Larger clusters ([Au(H2O)9-10]+) exhibit droplet-like formations with distorted rings, and show comparable binding energies for n=7-10.
• A significant charge migration from Au+ to outer water molecules was observed, indicating a screening effect.

Conclusions:

• The study reveals a distinct structural evolution of [Au(H2O)n]+ clusters, transitioning from simple coordination to complex ring and droplet-like structures.
• Quantum effects play a role in the nucleation process at small cluster sizes.
• The observed charge migration highlights an interesting electronic screening mechanism in hydrated metal cation clusters.