Slow dynamics of salol: a pressure and temperature dependent light scattering study

TL;DR

This study investigates the slow dynamics of salol under varying temperature and pressure using light scattering and thermodynamic measurements, validating entropy-based models and revealing a superposition principle in relaxation behavior.

Contribution

It provides experimental validation for entropy-based relaxation models and demonstrates a superposition principle in salol's structural relaxation under combined temperature and pressure variations.

Findings

Pressure data are essential for model validation.

Entropy-based equation accurately describes relaxation.

Time-temperature-pressure superposition holds.

Abstract

We study the slow dynamics of salol by varying both temperature and pressure using photon correlation spectroscopy and pressure-volume-temperature measurements, and compare the behavior of the structural relaxation time with equations derived within the Adam-Gibbs entropy theory and the Cohen-Grest free volume theory. We find that pressure dependent data are crucial to assess the validity of these model equations. Our analysis supports the entropy-based equation, and estimates the configurational entropy of salol at ambient pressure ? 70% of the excess entropy. Finally, we investigate the evolution of the shape of the structural relaxation process, and find that a time-temperature-pressure superposition principle holds over the range investigated.