Aggregation of a quenched Lennard-Jones system under shear
- Thermophysics Division, National Institute of Standards and Technology, Boulder, Colorado 80303 (United States)
- Research School of Chemistry, Australian National University, Canberra, ACT0200 (Australia)
The thermodynamic decomposition of an unstable thermostatted system of Lennard-Jones disks is investigated by nonequilibrium molecular dynamics. The system, first unsheared and then subjected to planar Couette flow, is studied after temperature quenches into the unstable vapor-liquid and the vapor-solid coexistence regions of the phase diagram. An interconnected morphology, characteristic of spinodal decomposition, forms after quenching. The cluster growth is found to be temporally self-similar, and the structure factor {ital S}({ital q},{ital t}) obeys the dynamic scaling relation {ital S}({ital q},{ital t}){approximately}{ital q}{sub {ital m}}{sup {minus}{ital d}{sub {ital f}}}({ital t}){tilde {ital S}}[{ital q}/{ital q}{sub {ital m}}({ital t})]. Here, {ital q} is the scattered wave vector magnitude, {ital q}{sub {ital m}}({ital t}) is the location of the low angle peak in {ital S}({ital q},{ital t}), {tilde {ital S}}({ital x}) is a time-independent structure function which has a maximum at {ital x}=1, and {ital d}{sub {ital f}} is a fractal dimension. {ital d}{sub {ital f}} is relatively insensitive to the postquench state point, but may depend on the shear rate. The primary influence of shear is to accelerate the aggregation{emdash}an effect that has also been observed experimentally in dense gelling silica suspensions. The similarities between these simulations and experiment suggest that a characteristic fractal dimension of a dense gel may be determined from measurements of {ital S}({ital q},{ital t}). {copyright} {ital 1996 The American Physical Society.}
- OSTI ID:
- 434551
- Journal Information:
- Physical Review, B: Condensed Matter, Vol. 53, Issue 5; Other Information: PBD: Feb 1996
- Country of Publication:
- United States
- Language:
- English
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