S. Ravichandran et B. Bagchi, MOLECULAR-DYNAMICS SIMULATIONS OF ORIENTATIONAL RELAXATION IN DIPOLARLATTICE - LACK OF DIFFUSIVE DECAY FOR 2ND AND HIGHER RANK CORRELATION-FUNCTIONS, Journal of physical chemistry, 98(44), 1994, pp. 11242-11245
Extensive molecular dynamics simulations have been carried out to calc
ulate the orientational correlation functions C-l(t), C-l(t) = [4 pi/(
2l + 1)]Sigma(m=-l)(l) [Y(lm)(Omega(0)) Y-lm(Omega(t))] (where Y-lm(O
mega) are the spherical harmonics) of point dipoles in a cubic lattice
. The decay of C-1(t) is found to be strikingly different from higher
l-correlation functions-the latter do not exhibit diffusive dynamics e
ven in the long time. Both the cumulant expansion expression of Lynden
-Bell and the conventional memory function equation provide very good
description of the C-1(t) in the short time but fail to reproduce the
observed slow, long time decay of C-1(t).