Solvent Isotherms and Structural Transitions in Nanoparticle Superlattice Assembly.

Area of Science:

• Thermodynamics
• Materials Science
• Nanotechnology

Background:

• Nanoparticle superlattices exhibit complex thermodynamic behavior influenced by solvent content.
• Predicting free energies and phase transitions in these systems is crucial for material design and assembly.
• Existing theories may not fully capture the behavior of compressible fluids within superlattices.

Purpose of the Study:

• Introduce a novel Molecular Theory for Compressible Fluids (MOLT-CF).
• Enable computation of thermodynamic functions for nanoparticle superlattices across all solvent contents.
• Validate the theory against molecular dynamics simulations and experimental findings.

Main Methods:

• Development of the Molecular Theory for Compressible Fluids (MOLT-CF).
• United-atom molecular dynamics simulations for validation.
• Application of MOLT-CF to analyze solvent content, phase transitions, and stability of nanoparticle superlattices.

Main Results:

• MOLT-CF shows quantitative agreement with molecular dynamics simulations.
• Solvent content in superlattices decreases linearly with vapor pressure.
• Predicts fcc-to-bcc Bain transitions and identifies the C14 Frank-Kasper phase as a metastable state.

Conclusions:

• MOLT-CF provides a reliable framework for predicting nanoparticle superlattice thermodynamics.
• The theory offers insights into solvent-drying effects and phase stability.
• Enables precise assembly and prediction of multicomponent nanoparticle systems.