Authors: A. Oprisan, S.A. Oprisan, A. Teklu, J. Hegseth
Affilation: College of Charleston, United States
Pages: 654 - 657
Keywords: structure factor, radial correlation function, nanocolloids, pure fluids
The direct visualization and analysis of critical fluctuations in pure fluids in microgravity, and concentration-driven interface fluctuations in nanocolloids provide invaluable information about cooperative phenomena and the role played by fluctuations in mixing, phase separation, and crystallization. Both in critical fluids in microgravity and in nanocolloids on Earth there are long-range correlations leading to phase separation, respectively, giant concentration-driven fluctuations. Small angle scattering is one of the most important techniques for studying fluctuations and phase separation involving structures that are in the size range up to a hundred nanometers. The static structure factor is the Fourier transformed pair correlation function, which describes the arrangement of the particles in real space. Although the structure factor is a statistical average representation of interaction potential among particles it still can be used to infer viable microscopic theoretical and computational models of nonequilibrium systems. By using these two sets of experimental data we investigated possible similarities between the effective interaction potentials determined by the long-range interactions taking place near critical point and those responsible for giant concentration-driven fluctuations in nanocolloids. For this purpose, the static structure factor, S(q), was determined from two-dimensional snapshots q of the sample cell. Our goal was to draw universal – material independent – conclusions regarding long range fluctuations near critical point in pure fluids and concentration-driven interface fluctuations in nanocolloids on Earth by solving the inverse problem – extract microscopic interaction potentials from structure factor.