Microscopic dynamics in the liquid Li-Na alloy: an ab initio molecular dynamics study

Area of Science:

• Condensed Matter Physics
• Materials Science
• Computational Chemistry

Background:

• Liquid alloys exhibit complex structural and dynamical behaviors.
• Understanding these properties is crucial for materials design and applications.
• Lithium-Sodium (Li-Na) alloys are technologically relevant systems.

Purpose of the Study:

• To investigate the structural and dynamical properties of liquid Li(1-x)Na(x) alloy.
• To compare computational results with available experimental data.
• To analyze the sound dispersion and identify different sound modes.

Main Methods:

• Orbital-free ab initio molecular dynamics.
• Local ionic pseudopotentials within the same framework.
• Calculation of partial dynamic structure factors.

Main Results:

• Accurate reproduction of experimental data, including strong homocoordinating tendencies.
• Identification of side peaks in partial dynamic structure factors.
• Observation of hydrodynamic sound dispersion at low wavevectors (q<=0.25 A(-1)).
• Identification of fast and slow sound modes at larger wavevectors.
• The Li-Na system, with a mass ratio of ~3, is the smallest mass ratio system where a fast sound mode is observed.

Conclusions:

• The orbital-free ab initio molecular dynamics method accurately describes the liquid Li-Na alloy.
• The alloy exhibits distinct sound modes, providing insights into its collective excitations.
• The observation of a fast sound mode in a low mass-ratio system advances the understanding of dynamic properties in liquid alloys.