On the Density Scaling of Liquid Dynamics
Abstract
Superpositioning of relaxation data as a function of the product variable TV gamma , where T is temperature, V the specific volume, and gamma a material constant, is an experimental fact demonstrated for approximately 100 liquids and polymers. Such scaling behavior would result from the intermolecular potential having the form of an inverse power law (IPL), suggesting that an IPL is a good approximation for certain relaxation properties over the relevant range of intermolecular distances. However, the derivation of the scaling property of an IPL liquid is based on reduced quantities, for example, the reduced relaxation time equal to T(exp 1/2V-1/3) times the actual relaxation time. The difference between scaling using reduced rather than unreduced units is negligible in the supercooled regime; however, at higher temperature the difference can be substantial, accounting for the purported breakdown of the scaling and giving rise to different values of the scaling exponent. Only the gamma obtained using reduced quantities can be sensibly related to the intermolecular potential.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2011
- Accession Number
- ADA549978
Entities
People
- C. Michael Roland
- D. Fragiadakis
Organizations
- United States Naval Research Laboratory