Structure formation under steady-state isothermal planar elongational flow of n-eicosane: a comparison between simulation and experiment.

We use nonequilibrium molecular dynamics simulations to investigate the structural properties of an oriented melt of n-eicosane under steady-state planar elongational flow. The flow-induced structure was evaluated using the structure factor s(k) taken as the Fourier transform of the total pair correlation function g(r). We found that the equilibrium liquid structure factor is in excellent agreement with the one determined via x-ray diffraction. Moreover, a new x-ray diffraction experiment has been performed on a crystalline n-eicosane sample. The resulting intramolecular contribution to the structure factor was found to be in very good agreement with the simulated one at a high elongation rate, indicating the existence of a possible crystalline precursor structure.