Liquid crystal seed nucleates liquid-solid phase change in ceria nanoparticles.

Area of Science:

• Materials Science
• Nanotechnology
• Physical Chemistry

Background:

• Understanding phase transitions in nanoparticles is crucial for materials science.
• Ceria nanoparticles are of interest due to their catalytic and optical properties.
• The crystallization process in nanomaterials can differ significantly from bulk materials.

Purpose of the Study:

• To investigate the liquid-solid phase change of a cerium oxide (ceria) nanoparticle.
• To determine the nature of the crystalline seed during nanoparticle crystallization.
• To explore the generalizability of observed phenomena beyond ceria nanoparticles.

Main Methods:

• Utilized molecular dynamics (MD) simulations to model the phase transition.
• Analyzed latent heat liberation during solidification.
• Measured cerium ion mobility within the nanoparticle.
• Calculated radial distribution functions (RDF) to assess structural order.

Main Results:

• The crystalline seed was identified as liquid, not solid, during nucleation.
• Latent heat release was minimal (3%) during initial crystallization (25%).
• Cerium ion mobility in the seed matched amorphous regions until 25% crystallization.
• Radial distribution functions indicated a lack of long-range order at 25% crystallization.

Conclusions:

• The crystallization of ceria nanoparticles initiates from a liquid seed.
• This liquid crystal seed behavior challenges traditional solidification models.
• The findings suggest that liquid crystal seeds may be a general phenomenon in nanoparticle crystallization.