Surface-induced crystallization in supercooled tetrahedral liquids.

Area of Science:

• Materials Science
• Physical Chemistry
• Computational Physics

Background:

• Solid-liquid phase transformations are significantly influenced by surfaces.
• Surface-induced crystallization is rarely observed, with few documented examples in specific materials.
• Understanding nucleation mechanisms is crucial for controlling material properties.

Purpose of the Study:

• To provide direct computational evidence of surface-induced nucleation in supercooled liquid silicon and germanium.
• To elucidate the role of free surfaces in the freezing of tetrahedral liquids with negative melting slopes.
• To investigate atomistic insights into semiconductor nucleation and its implications for other systems.

Main Methods:

• Molecular dynamics simulations were employed to model supercooled liquid silicon and germanium.
• The study focused on systems exhibiting a negative slope of their melting lines (dT/dP|coexist<0).
• Nucleation rates in the presence and absence of free surfaces were compared.

Main Results:

• Direct computational evidence of surface-induced nucleation was observed in liquid silicon and germanium.
• The presence of free surfaces was found to enhance nucleation rates by several orders of magnitude compared to bulk freezing.
• The findings highlight the critical role of surfaces in the freezing process of these specific tetrahedral liquids.

Conclusions:

• Free surfaces play a crucial role in initiating and accelerating the freezing process of supercooled silicon and germanium.
• The study supports the hypothesis of surface-induced crystallization in other tetrahedrally coordinated systems, including atmospheric water.
• These findings offer atomistic-level understanding relevant to semiconductor manufacturing and atmospheric science.