Abstract
.This paper addresses a computational method aimed at obtaining the isothermal compressibility of ferrofluids by means of molecular dynamics (MD) simulations. We model ferrofluids as a system of dipolar soft spheres and carry out MD simulations in the NPT ensemble. The obtained isothermal compressibility computed via volume fluctuations provides us with a strong evidence that dipolar interactions lead to a higher compressibility of dipolar soft sphere systems: the stronger the dipolar interactions, the bigger is the deviation of the compressibility from the one of a system with no dipoles. Furthermore, we use the isothermal compressibility to calculate the structure factor of ferrofluids at low values of wave vectors, i.e. in the range where it is difficult to predict its behaviour because of a problem with accounting for long-range particle correlations that give the main contribution to the structure factor in this range. Our approach based on the interpolation of the structure factor and the computed isothermal compressibility allows us to obtain the smooth structure factor in the range of low wave vectors and the reliable fractal dimension of the clusters formed in the system.Graphical abstract
Highlights
Nowadays many applications of soft matter heavily rely on the structural behaviour of their compounds
We observe the discrepancy between the methods which grows with increasing particle concentration: the compressibility calculated via radial distribution function (RDF) is consistently lower than its counterpart at a given density because of the finite size effect of the system in N V T simulations which has been enhanced by integration in eq (5)
This paper is aimed at computing the isothermal compressibility of dipolar soft sphere systems using computer simulations
Summary
Nowadays many applications of soft matter heavily rely on the structural behaviour of their compounds. The structural behaviour of these materials is usually very sensitive to both external stimuli and intrinsic characteristics of their compounds. One of the classical examples of dipolar soft matter materials with a large variety of phase and structural transitions is a ferrofluid, addressed sometimes as a magnetic fluid [1]. Ferrofluids represent a class of fluids consisting of single-domain magnetic particles suspended in a nonmagnetic liquid carrier. The scattering pattern obtained in these experiments transforms into a Contribution to the Topical Issue “Advances in Computational Methods for Soft Matter Systems” edited by Lorenzo Rovigatti, Flavio Romano, John Russo
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