Structure of polydisperse inverse ferrofluids: Theory and computer simulation

TL;DR

This paper combines theoretical analysis and molecular dynamics simulations to explore how polydispersity influences the structure of inverse ferrofluids, revealing that size distribution affects crystal formation and stability.

Contribution

It provides an analytical expression for interaction energy in polydisperse inverse ferrofluids and identifies body-centered tetragonal lattices as the ground state.

Findings

BCT lattices are energetically favored as ground states.

Polydispersity influences the formation of various structural configurations.

Size distribution can be tuned to fabricate specific colloidal crystals.

Abstract

By using theoretical analysis and molecular dynamics simulations, we investigate the structure of colloidal crystals formed by nonmagnetic microparticles (or magnetic holes) suspended in ferrofluids (called inverse ferrofluids), by taking into account the effect of polydispersity in size of the nonmagnetic microparticles. Such polydispersity often exists in real situations. We obtain an analytical expression for the interaction energy of monodisperse, bidisperse, and polydisperse inverse ferrofluids. Body-centered tetragonal (bct) lattices are shown to possess the lowest energy when compared with other sorts of lattices and thus serve as the ground state of the systems. Also, the effect of microparticle size distributions (namely, polydispersity in size) plays an important role in the formation of various kinds of structural configurations. Thus, it seems possible to fabricate colloidal crystals by choosing appropriate polydispersity in size.