Atomic structure evolution during solidification of liquid niobium from ab initio molecular dynamics simulations.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Materials Science

Background:

• Understanding atomic structure transitions is crucial for predicting material properties.
• Niobium's unique properties make it valuable in various high-temperature applications.
• Liquid and supercooled states present complex structural challenges.

Purpose of the Study:

• To investigate atomic structure transitions in liquid niobium during solidification.
• To analyze local atomic structure variations with temperature.
• To determine the dominant short-range order before crystallization.

Main Methods:

• Ab initio molecular dynamics simulations were employed.
• Temperatures ranged from 3200 K to 1500 K.
• Analysis included pair-correlation function, structure factor, bond-angle distribution, Honeycutt-Anderson index, Voronoi tessellation, and cluster alignment.

Main Results:

• Icosahedral short-range order was found to dominate in stable and supercooled liquid states.
• This icosahedral order persists until crystallization.
• The transition to the crystalline body-centered cubic phase occurred around 1830 K.

Conclusions:

• The study reveals a significant icosahedral short-range order in liquid and supercooled niobium.
• This structural characteristic precedes the transformation to the body-centered cubic phase.
• Simulation results provide insights into niobium's solidification behavior.