Two-step melting of Na(41)(+).

Area of Science:

• Physical Chemistry
• Materials Science
• Nanotechnology

Background:

• Previous studies on sodium-41 (Na41+) clusters suggested a smooth heat capacity curve, indicating a second-order melting transition without premelting.
• The absence of observable structure in earlier experiments limited the understanding of phase transitions in these clusters.

Purpose of the Study:

• To investigate the heat capacity of mass-selected Na41+ clusters with higher precision.
• To identify and characterize any structural features in the heat capacity curve that might indicate premelting or solid-solid transitions.
• To compare findings with previous experimental results and elucidate discrepancies.

Main Methods:

• Utilized a differential nanocalorimetry method for precise heat capacity measurements of Na41+ clusters.
• Employed mass selection to ensure the study focused specifically on Na41+ ions.
• Analyzed the heat capacity curve for distinct peaks or anomalies.

Main Results:

• Observed a distinct two-peak structure in the heat capacity curve of Na41+.
• Attributed the two peaks to melting and premelting phenomena.
• Identified a lower-temperature peak likely corresponding to an anti-Mackay to Mackay solid-solid transition.

Conclusions:

• The enhanced accuracy of differential nanocalorimetry reveals complex phase behavior in Na41+ clusters, including premelting.
• The observed solid-solid transition provides new insights into the structural dynamics of sodium clusters.
• Findings challenge previous interpretations of Na41+ melting behavior, highlighting the importance of experimental precision.