The orientational-correlation time intercept in liquids

• Published in: The Journal of chemical physics 1986-01, Vol.84 (1), p.385-390
• Main Authors: EVANS, G. T, KIVELSON, D
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Physics; Structure of liquids; Structure of solids and liquids; crystallography; Theory and models of liquid structure
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.450148

We propose a theory for the zero viscosity (η) or infinite temperature (T) intercept (τ0) in the much used quasihydrodynamic expression τ2=τ0+(const)(η/T) for the second rank orientational correlation time (τ2). Whereas we associate the (η/T) term with the integral over the torque–torque correlation function, we attribute the origin of τ0 to the integral over the cross-correlation function between torques and kinetic or convective terms. We are unable to evaluate the time dependence of this cross-correlation function exactly, but if a Gaussian form is assumed, a negative value is obtained for τ0. Experimentally, τ0 is sometimes positive and sometimes negative, which suggests that a monotonic form for the time dependence of the cross-correlation function might be inadequate. Because we have not been able to evaluate this cross-correlation function our explanation must still be considered a conjecture.