Crystal Nucleation without Supersaturation.

Area of Science:

• Materials Science
• Physical Chemistry
• Crystallography

Background:

• Classical nucleation theory (CNT) explains crystal formation from vapor or solution via direct nucleus formation.
• CNT posits supersaturation is essential for direct vapor deposition of crystals.
• Existing models do not account for crystal formation under saturated vapor conditions.

Purpose of the Study:

• To experimentally demonstrate a two-step crystal deposition mechanism from vapor.
• To investigate crystal nucleation under saturated vapor conditions, challenging CNT.
• To explore alternative pathways for crystal formation on solid surfaces.

Main Methods:

• Experimental observation of crystal deposition from vapor.
• Utilizing surface cavities for condensation.
• Monitoring nucleation and growth in condensed phases.

Main Results:

• First experimental evidence of a two-step crystal deposition mechanism from saturated vapor.
• Crystal deposition observed without supersaturation, contradicting CNT predictions.
• Mechanism involves condensation of supercooled liquid in surface cavities, followed by crystal nucleation.

Conclusions:

• Crystal deposition can occur via a two-step process involving a liquid intermediate, even from saturated vapor.
• This finding expands our understanding of nucleation phenomena beyond classical theory.
• The mechanism may be relevant to atmospheric ice nucleation and biomineralization.