Size--sensitive melting characteristics of gallium clusters: Comparison of Experiment and Theory for Ga$_{17}{}^{+}$ and Ga$_{20}{}^{+}$

TL;DR

This study combines experiments and first-principles simulations to investigate the melting behavior of Ga$_{17}{}^{+}$ and Ga$_{20}{}^{+}$ clusters, revealing size-sensitive differences linked to their ground-state geometries.

Contribution

It provides a comparative analysis of experimental and theoretical melting characteristics of gallium clusters, highlighting the influence of geometric order on melting signatures.

Findings

Ga$_{17}{}^{+}$ melts without a specific heat peak.

Ga$_{20}{}^{+}$ exhibits a sharp melting peak.

Ground-state symmetry correlates with melting behavior.

Abstract

Experiments and simulations have been performed to examine the finite-temperature behavior of Ga$_{17}{}^{+}$ and Ga$_{20}{}^{+}$ clusters. Specific heats and average collision cross sections have been measured as a function of temperature, and the results compared to simulations performed using first principles Density--Functional Molecular--Dynamics. The experimental results show that while Ga$_{17}{}^{+}$ apparently undergoes a solid--liquid transition without a significant peak in the specific--heat, Ga$_{20}{}^{+}$ melts with a relatively sharp peak. Our analysis of the computational results indicate a strong correlation between the ground--state geometry and the finite--temperature behavior of the cluster. If the ground--state geometry is symmetric and "ordered" the cluster is found to have a distinct peak in the specific--heat. However, if the ground--state geometry is amorphous or "disordered" the cluster melts without a peak in the specific--heat.