2003/11/28 by V. Ballenegger, J. P. Hansen, J.-P. Hansen
Chemistry · Engineering · Physics and Astronomy · #Characterization and Applications of Magnetic Nanoparticles #Electrohydrodynamics and Fluid Dynamics #Electrostatics and Colloid Interactions #cond-mat.soft #cond-mat.stat-mech
paper · pdf · doi:10.1080/00268970410001675554
10 pages, 11 figures; Paper submitted to Molecular Physics
arxiv created 2003/11/28 · openalex publication_date 2004/03/20 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/29
The strengths and shortcomings of the point dipole model for polar fluids of spherical molecules are illustrated by considering the physically more relevant case of extended dipoles formed by two opposite charges ± q separated by a distance d (dipole moment μ=qd). Extensive molecular dynamics simulations on a high-density dipolar fluid are used to analyse the dependence of the pair structure, dielectric constant ε and dynamics as a function of the ratio d/σ (σ is the molecular diameter), for a fixed dipole moment μ. The point dipole model is found to agree well with the extended dipole model up to d/σ ≃ 0.3. Beyond that ratio, ε shows a non-trivial variation with d/σ. When d/σ > 0.6, a transition is observed towards a hexagonal columnar phase; the corresponding value of the dipole moment is found to be substantially lower than the value of the point dipole required to drive a similar transition.