Ionic mixtures in two dimensions: From regular to empty crystals
Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf Universitätsstrasse 1, D-40225 Düsseldorf, Germany, EU
Accepted: 11 January 2010
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.
PACS: 64.70.kp – Ionic crystals / 61.50.Ah – Theory of crystal structure, crystal symmetry; calculations and modeling / 82.70.Dd – Colloids
© EPLA, 2010