Phase diagram of crystals of dusty plasma

Abstract

Dust particles effectively charged by plasma recently have been optically observed to exhibit crystalline phases not expected of Wigner or Yukawa crystals. Under varying conditions the crystal sometimes appears as deformed and oriented three-dimensional close-packed lattices of bcc, fcc, or hcp type, but mostly as a triangular array of vertical chains of particles. The unusual phases are shown to be caused by dipole-dipole interactions. The dipole moments are induced on the dust particles by gravity and by drag forces generated by ion stream. We describe in detail stable lattice structures and present the highly complex phase diagram of the dusty plasma. It turns out that in large parts of the phase diagram the stable phases indeed correspond to chains, but particles in neighboring chains belong to different sublattices. The stability of the lattices against excitations due to compression ͑i.e., aspect ratio variations͒ and vibration ͑i.e., phonons or charge density waves͒ is established. ͓S1063-651X͑97͒07409-6͔

Molecular dynamics simulations of dipolar dusty plasmas

“…For po = 0, the system crystalizes in an bct(ll0) structure. As po increases, the structure changes from Rh2 (b = 0.01) to R2 (po = 0.025) to Tl (po = O.l), where we use the notation of Lee et al (17). The Rh2 structure may also be described as a bct (1 10) lattice.…”

“…More generally, the dipole model can also take into account the intrinsic polarization of the grains interacting with the sheath electric field (16). Recently, Lee et al (17) have included a dipole moment to calculate the energy of a dusty plasma crystal and obtain a phase diagram as a h c t i o n of lattice spacing and the magnitude of the dipole contribution relative to the monopole force. For increasing dipole moment, they find non-close packed lattice structures that exhibit a linear chain structure along the axis of the dipole orientation.…”

Experimental Study of Coulomb Crystallization in Dusty Plasma

“…We attribute this to an electric field induced dipole-dipole interaction between the grains. This possibility has been proposed recently by an analysis of the phase diagram of such crystals [22]. We first give experimental results and then discuss our phenomenological model.…”

“…The temperature of the plasma was calculated from the slopes of the /-Fcharacterstics near the zero-current point [19]. The electron temperature into account screening by the background plasma, is given by [22]:…”

The Anisotropic Cell Model in the Colloidal Plasmas

“…To our knowledge, there are three kinds of physical mechanisms proposed to explain the formation of a dipole: (a) Field-induced dipole which is derived from dielectric polarization produced by the nearby charged object and the external field [28][29][30][31][32][33][34][35][36][37]; (b) compound-dipole which is caused by displacement of the centers of macroparticle charge and microion clouds (deformed sheath or double layer), it means that the macroparticle charge and the microion cloud charge form two poles of dipole [38][39][40][41][42][43]; (c) charging-resulted dipole which is caused by the nonuniform distribution of surface charge of macroparticles [44][45][46][47][48]. Whatever the reason for the formation of the dipole, the dipole or the macroparticle is in anisotropic microion cloud.…”