The Structure of Adamantane Clusters: Atomistic vs. Coarse-Grained Predictions From Global Optimization

Area of Science:

• Computational Chemistry
• Materials Science
• Condensed Matter Physics

Background:

• Adamantane clusters are molecular assemblies with potential applications in materials science.
• Understanding their structural evolution and stability is crucial for predicting their properties.

Purpose of the Study:

• To determine the lowest-energy structures (global minima) of adamantane clusters.
• To investigate the growth patterns and structural transitions in adamantane clusters up to N=42.
• To compare computational findings with experimental mass spectrometry data.

Main Methods:

• Employed a rigid molecular model with Lennard-Jones and Coulomb interactions.
• Utilized the basin-hopping method to explore the conformational space and identify low-energy structures.
• Performed coarse-graining of the intermolecular potential to assess its impact on structural predictions.

Main Results:

• Adamantane clusters exhibit an initial icosahedral packing for small N, transitioning to face-centered cubic structures above N=14.
• Identified specific cluster sizes (N=13, 19, 38) with enhanced stability ('magic numbers').
• Coarse-graining partially confirmed results but failed to capture transition details due to molecular anisotropy.

Conclusions:

• The study elucidates the fundamental growth mechanisms and structural preferences of adamantane clusters.
• Computational predictions align well with experimental observations of magic numbers in mass spectrometry.
• Highlights the importance of molecular anisotropy in accurately modeling cluster structures.