6 research outputs found
Stable crystalline lattices in two-dimensional binary mixtures of dipolar particles
The phase diagram of binary mixtures of particles interacting via a pair
potential of parallel dipoles is computed at zero temperature as a function of
composition and the ratio of their magnetic susceptibilities. Using lattice
sums, a rich variety of different stable crystalline structures is identified
including structures. [ particles correspond to large (small)
dipolar moments.] Their elementary cells consist of triangular, square,
rectangular or rhombic lattices of the particles with a basis comprising
various structures of and particles. For small (dipolar) asymmetry
there are intermediate and crystals besides the pure and
triangular crystals. These structures are detectable in experiments on granular
and colloidal matter.Comment: 6 pages - 2 figs - phase diagram update
Crystal nuclei and structural correlations in two-dimensional colloidal mixtures: experiment versus simulation
We examine binary mixtures of superparamagnetic colloidal particles confined
to a two-dimensional water-air interface both by real-space experiments and
Monte-Carlo computer simulations at high coupling strength. In the simulations,
the interaction is modelled as a pairwise dipole-dipole repulsion. While the
ratio of magnetic dipole moments is fixed, the interaction strength governed by
the external magnetic field and the relative composition is varied. Excellent
agreement between simulation and experiment is found for the partial pair
distribution functions including the fine structure of the neighbour shells at
high coupling. Furthermore local crystal nuclei in the melt are identified by
bond-orientational order parameters and their contribution to the pair
structure is discussed
Dynamical correlations and collective excitations of Yukawa liquids
In dusty (complex) plasmas, containing mesoscopic charged grains, the
grain-grain interaction in many cases can be well described through a Yukawa
potential. In this Review we summarize the basics of the computational and
theoretical approaches capable of describing many-particle Yukawa systems in
the liquid and solid phases and discuss the properties of the dynamical density
and current correlation spectra of three- and two-dimensional strongly coupled
Yukawa systems, generated by molecular dynamics simulations. We show details of
the dispersion relations for the collective excitations in these
systems, as obtained theoretically following the quasilocalized charge
approximation, as well as from the fluctuation spectra created by simulations.
The theoretical and simulation results are also compared with those obtained in
complex plasma experiments.Comment: 54 pages, 31 figure
Ionic mixtures in two dimensions: From regular to empty crystals
The ground state of a two-dimensional ionic mixture at zero pressure composed of oppositely charged spheres is determined as a function of the size asymmetry by using a penalty method. The cascade of stable structures includes square, triangular and rhombic crystals as well as “empty” crystals made up of dipoles and chains, which have a vanishing number density. Thereby we confirm the square structure, found experimentally on charged granulates, and predict new phases detectable in experiments on granular and colloidal matter