Diffusion in monodisperse ferrofluids

Peredo-Ortíz, R.; Hernández-Contreras, M.; Gómez, Raquel Hernández

doi:10.1088/1742-6596/792/1/012099

Cited by 3 publications

(11 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Moreover, they ignore the molecular degrees of freedom of position and orientation coordinates and momenta. They are coupled to the thermally driven solvent random forces f 0 and torques t 0 by fluctuationdissipation theorems [32][33][34]. The total force and torque F, T on the tracer by the rest of the colloidal particles, which are at the concentration nr…”

Section: Experimental Structure Factors and Diffusion Coefficientsmentioning

confidence: 99%

“…The measured structure factor provides the microscopic arrangements of particles accurately. Here, we provide a Langevin stochastic approach that allows the determination of the translational and rotational diffusion of the particles in ferrofluids [32,33]. These dynamic properties, in turn, allow quantifying the viscoelastic and dielectric moduli of the structural evolution of the fluid toward their equilibrium states [34].…”

Section: Introductionmentioning

confidence: 99%

“…Explicit statistical mechanics derivations for the dynamical collective correlation functions (intermediate scattering function) have been given that fit well Brownian dynamics simulations just at long wave numbers but fail at intermediate and short k values. In Refs [32][33][34],. we proposed a Langevin equation theory for a tracer ferroparticle whose motion is coupled to the cloud of the other colloidal magnetic particles with which it interacts.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Equilibrium Structures and Stationary Patterns on Magnetic Colloidal Fluids

Ortíz¹,

Contreras²,

Gómez³

2020

Pattern Formation and Stability in Magnetic Colloids

View full text Add to dashboard Cite

In this chapter, we review the experimental and theoretical modeling of structural and dynamical properties of colloidal magnetic fluids at equilibrium. Presently, several prototype experimental systems are very well characterized. We survey the different models, which help to reach a comprehensive knowledge of these complex magnetic fluids. One prime example is the ongoing investigation of the realistic interparticle potentials that drive the formation of the different phase states observed experimentally. Further, a stochastic equation approach for the description of tracer diffusion, viscoelasticity, and dielectric relaxation at equilibrium in colloidal ferrofluids is discussed.

show abstract

Section: Experimental Structure Factors and Diffusion Coefficientsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Equilibrium Structures and Stationary Patterns on Magnetic Colloidal Fluids

Ortíz¹,

Contreras²,

Gómez³

2020

Pattern Formation and Stability in Magnetic Colloids

View full text Add to dashboard Cite

show abstract

“…Furthermore, for a polydisperse interacting ferrofluid, its DMS bears a hierarchical structure [6] similar to Eqs. ( 39) and (40). It involves a single static correlation factor but a multitude of dynamic correlation factors, each of which corresponds to a distinct type of bare particles (distinguished by hydrodynamic volume, magnetic moment, or surface roughness).…”

Section: Static and Dynamic Orientational Correlation Factorsmentioning

confidence: 99%

“…There are few studies exploring the effects of dynamic correlations in ferrofluids. By employing the generalized Langevin equation approach [39,40], Hernández-Contreras et. al.…”

Section: Effects Of Dynamic Correlations In Ferrofluids a Concentrati...mentioning

confidence: 99%

Dynamical Effective Field Model for Interacting Ferrofluids: II. The proper relaxation time and effects of dynamic correlations

Fang¹

2020

Preprint

View full text Add to dashboard Cite

The recently proposed dynamical effective field model (DEFM) is quantitatively accurate for describing dynamical magnetic response of ferrofluids. In paper I it is derived under the framework of dynamical density functional theory (DDFT) and generalized to the cases with inhomogeneous density distribution or polydispersity. Employing a phenomenological description of nonadiabatic effects beyond the regular DDFT, the original ensemble of bare Brownian particles is mapped to an ensemble of dressed particles. However, it remains to clarify how the characteristic rotational relaxation time of a dressed particle, denoted by τ r , is quantitatively related to that of a bare particle, denoted by τ 0 r . By building macro-micro connections via two different routes, I reveal that under some gentle assumptions well satisfied in typical monodisperse ferrofluids, τ r can be identified with the mean relaxation time characterizing long-time rotational self-diffusion. I further introduce two simple but useful integrated correlation factors, describing the effects of quasi-static (adiabatic)and dynamic (nonadiabatic) inter-particle correlations, respectively. The former is determined by the ratio of static magnetic susceptibility for a correlated ferrofluid to that for a uncorrelated one, while the latter is determined by τ r /τ 0 r . In terms of both correlation factors I reformulate the dynamic magnetic susceptibility in an illuminating and elegant form. Remarkably, it shows that the macro-micro connection is established via two successive steps: a dynamical coarse-graining with nonadiabatic effects accounted for by the dynamic factor, followed by equilibrium statistical mechanical averaging captured by the static factor. Surprisingly, τ r /τ 0 r is found insensitive to changes of particle volume fraction. I provide a physical picture to explain it. Furthermore, an empirical formula is proposed to characterize the dependence of τ r /τ 0 r on dipole-dipole interaction strength.The DEFM supplemented with this formula leads to parameter-free predictions in good agreement with results from Brownian dynamics simulations. The theoretical developments presented in this paper may have important consequences to studies of ferrofluid dynamics in particular and other systems modelled by DDFTs in general.

show abstract

Dynamical effective field model for interacting ferrofluids: II. The proper relaxation time and effects of dynamic correlations

Fang¹

2021

J. Phys.: Condens. Matter

View full text Add to dashboard Cite

The recently proposed dynamical eﬀective ﬁeld model (DEFM) is quantitatively accurate for ferroﬂuid dynamics. It is derived in paper I within the framework of dynamical density functional theory (DDFT) along with a phenomenological description of nonadiabatic eﬀects. However, it remains to clarify how the characteristic rotational relaxation time of a dressed particle, denoted by τr, is quantitatively related to that of a bare particle, denoted by τr0. By building macro-micro connections via two diﬀerent routes, I reveal that under some gentle assumptions τr can be identiﬁed with the mean time characterizing long-time rotational self-diﬀusion. I further introduce two simple but useful integrated correlation factors, describing the eﬀects of quasi-static (adiabatic) and dynamic (nonadiabatic) inter-particle correlations, respectively. In terms of both the dynamic magnetic susceptibility is expressed in an illuminating and elegant form. Remarkably, it shows that the macro-micro connection is established via two successive steps: a dynamical coarse-graining with nonadiabatic eﬀects accounted for by the dynamic factor, followed by equilibrium ensemble averaging captured by the static factor. By analyzing data from Brownian dynamics simulations on monodisperse interacting ferroﬂuids, I ﬁnd τr/τr0 is, somehow unexpectedly, insensitive to changes of particle volume fraction. A physical picture is proposed to explain it. Furthermore, an empirical formula is proposed to characterize the dependence of τr/τr0 on dipole-dipole interaction strength. The DEFM supplemented with this formula leads to parameter-free predictions in good agreement with results from Brownian dynamics simulations. The theoretical developments presented in this paper may have important consequences to studies of ferroﬂuid dynamics in particular and other systems modelled by DDFTs in general.

show abstract

Diffusion in monodisperse ferrofluids

Cited by 3 publications

References 21 publications

Equilibrium Structures and Stationary Patterns on Magnetic Colloidal Fluids

Equilibrium Structures and Stationary Patterns on Magnetic Colloidal Fluids

Dynamical Effective Field Model for Interacting Ferrofluids: II. The proper relaxation time and effects of dynamic correlations

Dynamical effective field model for interacting ferrofluids: II. The proper relaxation time and effects of dynamic correlations

Contact Info

Product

Resources

About