Reinke D, Stark H, von Grünberg H-H, Schofield Andrew B, Maret G, Gasser U
Physics Department, University of Konstanz, 78457 Konstanz, Germany.
Phys Rev Lett. 2007 Jan 19;98(3):038301. doi: 10.1103/PhysRevLett.98.038301.
The elastic properties of fcc crystals consisting of charge stabilized colloidal particles are determined from real space imaging experiments using confocal microscopy. The normal modes and the force constants of the crystal are obtained from the fluctuations of the particles around their lattice sites using the equipartition theorem. We show that the Cauchy relation is not fulfilled and that only noncentral many-body forces can account for the elastic properties.