Precursors of order in aggregates of patchy particles

We study computationally the local structure of aggregated systems of patchy particles. By calculating the probability distribution functions of various rotational invariants we can identify the precursors of orientation order in amorphous phase. Surprisingly, the strongest signature of local order is observed for 4-patch particles with tetrahedral symmetry, not for 6-patch particles with the cubic one. This trend is exactly opposite to their known ability to crystallize. We relate this anomaly to the observation that a generic aggregate of patchy systems has coordination number close to 4. Our results also suggest a significant correlation between rotational order in the studied liquids with the corresponding crystalline phases, making this approach potentially useful for a broader range of patchy systems.Comment: 12 pages, 3 figure

Chromatic patchy particles: Effects of specific interactions on liquidă structure

International audienceWe study the structural and thermodynamic properties of patchy particleă liquids, with a special focus on the role of ``color,'' i.e., specifică interactions between individual patches. A possible experimentală realization of such ``chromatic'' interactions is by decorating theă particle patches with single-stranded DNA linkers. The complementarityă of the linkers can promote selective bond formation betweenă predetermined pairs of patches. By using MD simulations, we compare theă local connectivity, the bond orientation order, and other structurală properties of the aggregates formed by the ``colored'' andă ``colorless'' systems. The analysis is done for spherical particlesă with two different patch arrangements (tetrahedral and cubic). It isă found that the aggregated (liquid) phase of the ``colorless'' patchyă particles is better connected, denser and typically has stronger locală order than the corresponding ``colored'' one. This, in turn, makes theă colored liquid less stable thermodynamically. Specifically, we predictă that in a typical case the chromatic interactions should increase theă relative stability of the crystalline phase with respect to theă disordered liquid, thus expanding its region in the phase diagram

Collective modes in two-dimensional one-component-plasma with logarithmic interaction

The collective modes of a familiar two-dimensional one-component-plasma with the repulsive logarithmic interaction between the particles are analysed using the quasi-crystalline Approximation (QCA) combined with the molecular dynamic simulation of the equilibrium structural properties. It is found that the dispersion curves in the strongly coupled regime are virtually independent of the coupling strength. Arguments based on the excluded volume consideration for the radial Distribution function allow us to derive very simple expressions for the dispersion relations, which Show excellent agreement with the exact QCA dispersion over the entire domain of wavelengths. Comparison with the results of the conventional fluid analysis is performed, and the difference is explained

On the long-waves dispersion in Yukawa systems

International audienceA useful simplification of the quasilocalized charge approximations (QLCA) method to calculate the dispersion relations in strongly coupled Yukawa fluids is discussed. In this simplified version, a simplest possible model radial distribution function, properly related to the thermodynamic properties of the system, is used. The approach demonstrates good agreement with the dispersion relations obtained using the molecular dynamics simulations and the original QLCA in the long-wavelength regime. (C) 2016 AIP Publishing LLC

Fingerprints of different interaction mechanisms on the collective modes in complex (dusty) plasmas

International audienceIn this paper, we discuss the relations between the exact shape of interparticle interactions in complex (dusty) plasmas and the dispersion relation of the longitudinal collective mode. Several representative repulsive potentials, predicted previously theoretically, are chosen, and the corresponding dispersion relations are calculated using the quasi-crystalline approximation. Both weakly coupled and strongly coupled regimes are considered. It is shown that the long-wavelength portions of the dispersion curves can be sensitive to the long-range asymptote of the interaction potential. This can be used to discriminate between different interaction mechanisms operational in complex plasmas experimentally. Main requirements are briefly discussed. Published by AIP Publishing