First-principles investigation of finite-temperature behavior in small sodium clusters

Area of Science:

• Computational Physics
• Materials Science
• Physical Chemistry

Background:

• Understanding the finite-temperature behavior of small metal clusters is crucial for materials science.
• Previous experimental studies have shown complex melting behaviors in alkali metal clusters.

Purpose of the Study:

• To systematically investigate the finite-temperature properties of sodium clusters (Na(n)) for n=8-50.
• To analyze the size-dependent melting transitions and thermodynamic indicators of these clusters.

Main Methods:

• Density-functional molecular dynamics simulations were employed.
• Ultrasoft pseudopotentials were utilized for accurate electronic structure calculations.
• Thermodynamic indicators including specific heat and caloric curves were computed.

Main Results:

• Small sodium clusters (n=8, 10) did not exhibit melting transitions.
• A transition from solid-like to liquid-like behavior was observed with increasing cluster size, indicated by changes in specific heat peaks.
• Melting temperatures displayed irregular patterns, consistent with experimental observations, and a size-sensitive effect was noted around n=40-55.

Conclusions:

• The study demonstrates a clear evolution of melting behavior with increasing sodium cluster size.
• The findings highlight the complexity of phase transitions in finite systems and the importance of size effects.
• The observed irregular melting patterns and size-sensitive effects in sodium clusters align with experimental data for other metallic clusters.