Solvation dynamics in supercritical fluids: equilibrium versus nonequilibrium solvent response functions

Area of Science:

• Physical Chemistry
• Chemical Physics
• Thermodynamics

Background:

• Understanding solvation dynamics is crucial for chemical processes.
• Supercritical fluids exhibit unique solvent properties.
• Distinguishing equilibrium from nonequilibrium solvation is key.

Purpose of the Study:

• To theoretically investigate solvation dynamics in supercritical fluids.
• To analyze the differences between equilibrium and nonequilibrium solvent responses.
• To develop an accurate model for nonequilibrium solvation.

Main Methods:

• Conducting molecular dynamics simulations.
• Developing an analytical theory based on the generalized nonlinear Smoluchowski-Vlasov equation.
• Comparing theoretical predictions with simulation results.

Main Results:

• Significant differences observed between equilibrium and nonequilibrium solvent response functions, particularly at lower densities.
• The proposed analytical theory shows good agreement with molecular dynamics simulations.
• Accurate description of the time-dependent solvent density profile around a solute was achieved.
• Evidence of gradual solvent clustering around an excited solute in nonequilibrium conditions.

Conclusions:

• Nonequilibrium solvation effects are pronounced in supercritical fluids.
• The developed analytical theory provides a robust framework for understanding these dynamics.
• Solvent clustering is a key feature of nonequilibrium solvation in supercritical media.