Search results for "Condensed Matter::Soft Condensed Matter"
showing 10 items of 716 documents
Enhanced structural correlations accelerate diffusion in charge-stabilized colloidal suspensions
1999
Theoretical calculations for colloidal charge-stabilized and hard sphere suspensions show that hydrodynamic interactions yield a qualitatively different particle concentration dependence of the short-time self-diffusion coefficient. The effect, however, is numerically small and hardly accessible by conventional light scattering experiments. Applying multiple-scattering decorrelation equipment and a careful data analysis we show that the theoretical prediction for charged particles is in agreement with our experimental results from aqueous polystyrene latex suspensions.
Exotic crystal superstructures of colloidal crystals in confinement.
2008
Colloidal model systems have been used for over three decades for investigating liquids, crystals, and glasses. Colloidal crystal superstructures have been observed in binary systems of repulsive spheres as well as oppositely charged sphere systems showing structures well known from atomic solids. In this work we study the structural transition of colloidal crystals under confinement. In addition to the known sequence of crystalline structures, crystal superstructures with dodecagonal and hexagonal symmetry are observed in one component systems. These structures have no atomic counterpart.
Structure of metastable 2D liquid helium
2007
We present diffusion Monte Carlo (DMC) results on a novel, superfluid phase in two-dimensional 4He at densities higher than 0.065 A-2, which is very close to the freezing density. The new phase has anisotropic, hexatic orbital order, but the single-particle density remains constant. By increasing density the hexatic superfluid forms a metastable state, which lies above the crystal ground state in energy. This implies that the liquid-solid phase transition takes place in two stages: a second-order phase transition from the isotropic superfluid to the hexatic superfluid, followed by a first-order transition that localizes atoms into the triangular crystal order.
Colloid-polymer mixtures between asymmetric walls: Evidence for an interface localization transition
2007
We demonstrate via computer simulation that mixtures of colloids and polymers confined to thin films have the ability to undergo an interface localization transition. While one wall of the film is assumed to be hard for both particles, at the other wall, an additional repulsive potential acts, but on the colloids only. By varying the strength of this repulsion, a crossover from capillary condensation to interface localization is found. The latter occurs under conditions where in the bulk almost complete phase separation has occurred.
Dipolar and Quadrupolar Freezing in(KBr)1−x(KCN)x
1986
Dipolar and quadrupolar susceptibility measurements are reported for the molecular glass system ${(\mathrm{KBr})}_{1\ensuremath{-}x}{(\mathrm{KCN})}_{x}$ covering a wide range of frequencies. The results allow a direct comparison of the dipolar and quadrupolar anomalies and demonstrate unambiguously that the freezing in of the dipolar and quadrupolar degrees of freedom occurs at different temperatures.
Dynamics of thermally induced optical nonlinearity in GaSe thin slabs
1996
A study of the nonlinear effects shown by thin slabs of GaSe metaled with Au is presented.
Direct measurement of forces between particles and bubbles
1999
One of the elementary stages of the flotation process is the formation of an aggregate between the particle and a bubble. This aggregate formation is governed by hydrodynamic, capillary and interparticle forces. During the last four years, techniques have been developed to measure directly the force between a colloidal particle and a bubble. These techniques are closely related to the development of atomic force microscopy. Advantages and possibilities, as well as limits and drawbacks are described.
Theoretical modeling of Langmuir monolayers
1999
Abstract We study coarse-grained continuum models for Langmuir monolayers by self-consistent field theory and by Monte Carlo simulations. Amphiphilic molecules are represented by stiff chains of monomers with one end grafted to a planar surface. In particular, we discuss the origin of successive fluid–fluid transitions, the possible origin of tilt order and the factors which determine the direction of tilt.
Neutrons detect order in glasses
2005
The first glassy material was probably made in ancient Egypt some 4500 years ago, so the fact that the structure of glass is still one of the biggest puzzles in physics may come as a surprise. When a liquid is cooled very quickly, the atoms do not have time to arrange themselves into an ordered crystalline solid. Instead, the super cooled liquid falls out of equilibrium and into a disordered amorphous network, more commonly known as a glass.
Enthalpy of Solution of Nonionic Solutes in Organized Systems
1989
The standard enthalpies of solution of alcohols in micellar solutions of dodecyltrimethylammonium bromide were obtained by direct measurements and by enthalpies of mixing. The observed trends were analyzed with a previously reported model. From the resulting equations, the distribution constant, standard enthalpy of transfer from aqueous to the micellar phase and the standard enthalpy of solution in micellar phase can be calculated at the same time using a linear least-squares analysis. The model seems to hold well also in the case of short chain surfactants and microheterogeneities in spite of the fact that the micellization equilibrium is treated as a pseudo-phase transition.