Two-component dynamics in supercritical [Formula: see text] from inelastic X-ray scattering

Area of Science:

• Condensed matter physics
• Physical chemistry
• Materials science

Background:

• Supercritical fluids possess unique thermodynamic properties.
• A key property is two-component dynamics, marked by distinct low- and high-frequency vibrational responses.
• The origin of this two-component dynamics remains unclear.

Purpose of the Study:

• To investigate the origin of two-component dynamics in supercritical fluids.
• To establish a link between molecular clustering, density heterogeneities, and observed dynamics.

Main Methods:

• Combined inelastic X-ray scattering (IXS) and molecular dynamics (MD) simulations.
• Analysis of molecular trajectories and scattering data.

Main Results:

• Density heterogeneities, arising from molecular clusters, were identified.
• Distinct momentum fluctuations were observed between clustered and unbound molecules.
• These distinct fluctuations were directly correlated with the two-component dynamics.

Conclusions:

• The two-component dynamics in supercritical fluids originate from molecular clusters and associated density heterogeneities.
• Molecular-structural heterogeneity is crucial for understanding dynamics in supercritical fluids, colloids, and condensed matter.
• This finding provides insight into complex fluid behavior and material properties.