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Dynamic moduli of concentrated dispersions by Brownian dynamics

 

作者: P. B. Visscher,   P. J. Mitchell,   D. M. Heyes,  

 

期刊: Journal of Rheology  (AIP Available online 1994)
卷期: Volume 38, issue 3  

页码: 465-483

 

ISSN:0148-6055

 

年代: 1994

 

DOI:10.1122/1.550470

 

出版商: The Society of Rheology

 

关键词: COLLOIDS;BROWNIAN MOVEMENT;CRYSTALLIZATION;VISCOELASTICITY;DISPERSIONS;STRESS RELAXATION;SHEAR PROPERTIES;FREQUENCY DEPENDENCE;CORRELATION FUNCTIONS;OSCILLATIONS

 

数据来源: AIP

 

摘要:

The viscoelastic properties of model stable colloidal dispersions are calculated using Brownian dynamics simulations with a free‐draining model for the hydrodynamic interactions. In this report we describe a number of alternative routes to the dynamic moduli, making a comparison of the relative merits of the approaches. These include the use of the Green‐Kubo formulas (used widely by the molecular simulation community but little used so far in colloid modeling), which gives thelinearstress relaxation function from stress fluctuations in anunshearedmodel colloidal liquid. We also consider the direct application of an oscillating shear strain, as used in experiment, changing the frequency and strain amplitude in discrete jumps. This method is developed to consider a continuously varying sweep through frequency (constant strain amplitude) or strain amplitude (constant frequency). This route avoids problems associated with equilibration at each frequency. We avoid errors associated with truncation of the Fourier transform by cutting it off smoothly with a broad Gaussian. We concentrate on the real and imaginary parts of the complex storage modulusG*, the storage modulusG’, and loss modulusG‘, being the most frequently cited viscoelastic functions. For very large amplitudes, we find oscillatory‐shear‐induced crystallization to a fcc structure.

 

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