In-plane structure and ordering at liquid sodium surfaces and interfaces from ab initio molecular dynamics

Area of Science:

• Materials Science
• Physical Chemistry
• Computational Physics

Background:

• Atoms at liquid metal surfaces form ordered layers parallel to the surface.
• Understanding atomic arrangement is crucial for predicting material properties.

Purpose of the Study:

• To analyze the 2D atomic arrangement in liquid sodium surface layers.
• To investigate the influence of temperature on atomic coordination and ordering.

Main Methods:

• Ab initio molecular dynamics (MD) simulations based on density functional theory.
• Analysis of nearest neighbor and bond angle distributions.
• Comparison with classical MD simulations and ab initio simulations of solid-liquid interfaces.

Main Results:

• Liquid sodium surface atoms primarily show fivefold coordination.
• A tendency towards sixfold coordination and hexagonal arrangement is observed as temperature decreases.
• A distorted hexagonal model explains the mixed coordination states.

Conclusions:

• The atomic structure at liquid sodium surfaces is a mixture of five- and sixfold coordinated regions.
• Decreasing temperature promotes hexagonal ordering, anticipating solidification.
• Computational simulations provide detailed insights into surface atomic dynamics.