Equilibration and Aging of Liquids of Non-Spherically Interacting Particles

The nonequilibrium self-consistent generalized Langevin equation theory of irreversible processes in liquids is extended to describe the positional :and orientational thermal fluctuations of the instantaneous local concentration profile n(r,Omega,t) of a suddenly quenched colloidal liquid of particles interacting through nonspherically symmetric pairwise interactions, whose mean value <(n(r,Omega,t))over bar> is constrained to remain uniform and isotropic, (n) over bar (r,Omega,t) = (n) over bar. Such self-consistent theory is cast in terms of the time-evolution equation of the covariance sigma(t) = <(delta n(lm)(k; t)delta n(lm)dagger(k; t))over bar> of the fluctuations delta n(lm)(k; t) = n(lm)(k; t) - (n(lm)) over bar (k; t) of the spherical harmonics projections n(lm)(k; t) of the Fourier transform of n(r,Omega,t). The resulting theory describes the nonequilibrium evolution after a sudden temperature quench of both, the static structure factor projections S-lm(k,t) and the two-time correlation function F-lm(k, tau; t) equivalent to <(delta n(lm)(k; t)delta n(lm)(k, t + tau))over bar>, where tau is the correlation delay time and t is the "evolution or waiting time after the quench. As a concrete and illustrative application we use the resulting self-consistent equations to describe the irreversible processes of equilibration or aging of the orientational degrees of freedom of a system of strongly interacting classical dipoles with quenched positional disorder.