Ice formation on kaolinite: Insights from molecular dynamics simulations

Area of Science:

• Physical Chemistry
• Materials Science
• Geophysics

Background:

• Ice formation via heterogeneous nucleation is vital for technologies like cryopreservation.
• The molecular mechanisms of ice nucleation on foreign surfaces are not well understood.
• Atomistic simulations face challenges due to complex water-substrate interactions and long timescales.

Purpose of the Study:

• Investigate heterogeneous ice nucleation using molecular dynamics simulations.
• Examine the role of kaolinite, a clay mineral, as an ice nucleating material.
• Understand the influence of surface relaxation on kaolinite's ice nucleation ability.

Main Methods:

• Seeded molecular dynamics simulations.
• Analysis of water-kaolinite interface dynamics.
• Comparison of relaxed and non-relaxed kaolinite surface models.

Main Results:

• Ice nucleation on kaolinite’s hydroxylated (001) face exclusively forms hexagonal ice.
• The critical nucleus size for kaolinite nucleation is half that of homogeneous nucleation.
• Surface relaxation of kaolinite significantly alters its templating ability for hexagonal water overlayers, impacting nucleation.

Conclusions:

• Kaolinite's surface relaxation is a critical factor determining its ice nucleation efficiency.
• Small structural changes in kaolinite's surface dramatically influence heterogeneous ice formation.
• This study provides molecular-level insights into ice nucleation on mineral surfaces relevant to atmospheric science.