Intermolecular Distance And Density Scaling Of Dynamics In Molecular Liquids

A broad variety of liquids conform to density scaling: relaxation times can be expressed as a function of the ratio of temperature to density, the latter raised to a material constant gamma. For atomic liquids interacting only through simple pair potentials, the exponent gamma is very nearly equal to n/3, where n is the steepness of the intermolecular potential, while for molecular liquids having rigid bonds and built using the same interatomic potential, gamma > n/3. We find that for this class of molecular liquids, gamma = n/delta, where the parameter 6 relates the intermolecular distance to the density along an isomorph (the line of approximately constant dynamics and structure). 6 depends only on the molecular structure and not the interatomic potential. Published under license by AIP Publishing.