Related Experiment Video
Updated: Sep 6, 2025

Studying Large Amplitude Oscillatory Shear Response of Soft Materials
Published on: April 25, 2019
Comparison between longitudinal viscoelastic relaxation and sound dispersion of molecular liquids on the molecular
1Graduate School of Engineering, Nagoya University, Chikusa, Nagoya 464-8603, Japan.
Abstract:
Molecular dynamics simulation on some molecular liquids was performed to study sound dispersion on the molecular scale. The sound velocity was determined from the intermediate scattering function, and the relation between the longitudinal modulus and frequency was compared with the frequency-dependent longitudinal modulus in the q = 0 limit evaluated by the Kubo-Green theory. The sound dispersion of a monoatomic liquid up to qσ ≅ 2 was almost quantitatively explained by the viscoelasticity in the q = 0 limit when the wavenumber dependence of the heat capacity ratio was taken into account. The situation was similar for a polyatomic molecular liquid for which the intramolecular degrees of freedom were fixed. For a polyatomic liquid with intramolecular degrees of freedom, the sound dispersion on the molecular scale was connected to the high-frequency limit of the ultrasonic relaxation mode assigned to the vibrational energy relaxation. After subtracting the contribution of the vibrational energy relaxation, both the longitudinal viscoelasticity and the sound dispersion depended little on the presence of intramolecular degrees of freedom.
More Related Videos
10:28Experimental Measurement of Settling Velocity of Spherical Particles in Unconfined and Confined Surfactant-based Shear Thinning Viscoelastic Fluids
Published on: January 3, 2014
11:03An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids
Published on: December 4, 2017
Related Concept Videos
Speed of Sound in Solids and Liquids
Deriving the Speed of Sound in a Liquid
The speed of sound in fluids can be derived by considering a mechanical wave...
Atomic Nuclei: Types of Nuclear Relaxation
In spin–lattice or longitudinal relaxation, the excited spins exchange energy with the surrounding lattice as they return to the lower energy level. Among several mechanisms that contribute to spin–lattice relaxation, magnetic dipolar interactions are significant. Here, the excited nucleus transfers...
Molecular Comparison of Gases, Liquids, and Solids
IR Spectroscopy: Hooke's Law Approximation of Molecular Vibration
According to Hooke's law, the vibrational frequency is directly proportional to...
Viscosity of Fluid