Neutral and charged gallium clusters: structures, physical properties and implications for the melting features

Area of Science:

• Computational materials science
• Quantum chemistry
• Condensed matter physics

Background:

• Gallium nitride (GaN) clusters are crucial in materials science.
• Understanding their structure-property relationships is key for technological applications.
• Previous studies lacked detailed insights into global minimum structures and electronic properties.

Purpose of the Study:

• To determine the putative Global Minimum (GM) structures and electronic properties of Ga(N)(+), Ga(N), and Ga(N)(-) clusters for N = 13-37 atoms.
• To identify and interpret magic numbers in terms of electronic and geometric shell closings.
• To correlate theoretical findings with experimental data, including mass spectra, photoelectron spectra, and melting behaviors.

Main Methods:

• First-principles density functional theory (DFT) structural optimizations.
• Inclusion of spin polarization and van der Waals dispersion interactions (vdW-DFT).
• Analysis of structural motifs, electronic shell closings, and cohesive energies.

Main Results:

• Diverse structural motifs (decahedral, polyicosahedral, polytetrahedral, layered) were identified for GM structures.
• Cluster structures are highly sensitive to electron count, differing between neutral and charged states.
• Magic numbers were identified and explained by electronic and geometric shell closings, aligning with experimental data.
• Theoretical predictions successfully interpreted experimental observations of melting behavior and cluster shapes.

Conclusions:

• The study provides a comprehensive understanding of GaN cluster structures and stability.
• Electronic and geometric shell closings are critical factors determining cluster stability (magic numbers).
• The findings reconcile theoretical predictions with experimental results, offering insights into the unique properties of gallium clusters, including their higher-than-bulk melting temperatures.