Estimation of the nucleation barrier in a multicomponent system with intermolecular potential

Area of Science:

• Atmospheric Chemistry
• Aerosol Science
• Physical Chemistry

Background:

• New particle formation (NPF) is critical in atmospheric processes, involving the formation of "critical nuclei" before phase change.
• Nucleation below 1 nm is difficult to observe directly, necessitating theoretical models.
• Intermolecular interactions of typical nucleation agents like sulfuric acid (H₂SO₄), water (H₂O), and ammonia (NH₃) are significant.

Purpose of the Study:

• To investigate the nucleation barriers of H₂SO₄, H₂O, and NH₃ using a dipole-dipole potential model.
• To quantify the influence of H₂O and NH₃ on nucleation barriers and collision coefficients.
• To identify key factors affecting ternary nucleation and its atmospheric implications.

Main Methods:

• Employed a dipole-dipole potential model to describe molecular interactions, moving beyond the traditional hard sphere model.
• Utilized graph theory to analyze cluster structure and cluster-molecule interactions.
• Calculated nucleation barriers (ΔE_b) for various combinations of H₂SO₄, H₂O, and NH₃, including ternary systems.

Main Results:

• The presence of H₂O and NH₃ decreased nucleation barriers by 17-28% compared to pure H₂SO₄ nucleation.
• Ammonia (NH₃) was identified as a key factor in ternary nucleation.
• Effective collision coefficients (α) in ternary systems were 3-4 orders of magnitude higher than in pure H₂SO₄ systems, reaching (2.5-25) × 10⁻⁵.

Conclusions:

• Dipole-dipole interactions and cluster structure significantly influence atmospheric nucleation.
• Ammonia and water play crucial roles in reducing nucleation barriers and enhancing particle formation rates.
• Focusing on NH₃ and H₂O is recommended for future aerosol particle estimation and control strategies.