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Studies of the effects of particle-size polydispersity or of particle interactions on active matter have been limited to determine and analyze the system short-time dynamics in the high-density regime. On the other hand, the effects of polydispersity on the structural behavior of active systems are of relevance and have received much less attention. In this paper, we comprehensively analyze the effects of size dispersion of pseudo hard-disk active Brownian particles, on its structural behavior at different system densities and different self-propelling velocities, thus elucidating the interplay of these features with the polydispersity. This is introduced into our analysis by well-known particle size distributions in such a manner that the average size is fixed, but with a variance that accounts for different dispersion of the particle size according to: Gaussian, Weibull, uniform and "two point" distribution. Local and global structural properties of the system are determined under these considerations. We observe that activity and size polydisperse effects become relevantly conspicuous at densities above the motility induced phase separation critical point of the monodispersal fluid. We notice that, while the activity promotes a more defined local and global structural arrangement, the polydispersity decreases such structure, observing the greatest effect when the particle size is defined by a uniform distribution. [ABSTRACT FROM AUTHOR]

It has been both experimentally and theoretically observed that the structural and dynamical properties of glass-forming fluids can be scaled and described within the dynamic universality class of hard spheres. One of the key predictions of this universality is the long-time dynamic equivalence between Brownian and Molecular dynamics systems governed by the same kind of interaction potential. However, the application and extent of this principle has not been validated for two-dimensional systems. To this end, we employ Brownian and Molecular Dynamics simulations to validate this principle in the two-dimensional case, analysing the long-time properties of systems made up of monodisperse hard disks. By introducing a suitable density-dependent scaling factor, we successfully extend the principle of dynamic equivalence to two dimensions. This dynamic correspondence will facilitate the interpretation of long-time molecular dynamic properties in the context of colloidal dynamics. For instance, this correspondence will allow us to establish the extension of the colloidal freezing criterion to the molecular case. [ABSTRACT FROM AUTHOR]

In the same sense as in the extended law of corresponding states [M. Noro and D. Frenkel, J. Chem. Phys. 113, 2941 (2000)], we propose the use of the second virial coefficient to map the hard-sphere potential onto a continuous potential. We show that this criterion provides accurate results when the continuous potential is used, for example, in computer simulations to reproduce the physical properties of systems with hard-core interactions. We also demonstrate that this route is straightforwardly applicable to any spatial dimension, does not depend on the particle density and, from a numerical point of view, is easy to implement. [ABSTRACT FROM AUTHOR]

We present a systematic study of the self-diffusion coefficient for a fluid of particles interacting via the square-well pair potential by means of molecular dynamics simulations in the canonical (N, V, T) ensemble. The discrete nature of the interaction potential is modeled by the constant force approximation, and the self-diffusion coefficient is determined for several fluid densities at supercritical thermodynamic states. The dependence of the self-diffusion coefficient on the potential range λ is analyzed in the range of 1.1 ≤ λ ≤ 1.5. The obtained simulation results are in agreement with the self-diffusion coefficient predicted by the Enskog method. Additionally, we show that the diffusion coefficient is very sensitive to the potential range λ. Our results for the self-diffusion coefficient times density extrapolate well to the values in the zero-density limit obtained from the Chapman-Enskog theory for dilute gases. The constant force approximation used in this work to model the discrete pair potentials has shown to be an excellent scheme to compute the transport properties of square-well fluids using molecular dynamics simulations. Finally, the simulation results presented here are useful for improving theoretical approaches, such as the Enskog method. [ABSTRACT FROM AUTHOR]

A model for anomalous transport of tracer particles diffusing in complex media in two dimensions is proposed. The model takes into account the characteristics of persistent motion that an active bath transfers to the tracer; thus, the model proposed here extends active Brownian motion, for which the stochastic dynamics of the orientation of the propelling force is described by scaled Brownian motion (sBm), identified by time-dependent diffusivity of the form D_{β}∝t^{β-1}, β>0. If β≠1, sBm is highly nonstationary and suitable to describe such nonequilibrium dynamics induced by complex media. In this paper, we provide analytical calculations and computer simulations to show that genuine anomalous diffusion emerges in the long-time regime, with a time scaling of the mean-squared displacement t^{2-β}, while ballistic transport t^{2}, characteristic of persistent motion, is found in the short-time regime. We also analyze the time dependence of the kurtosis, and the intermediate scattering function of the position distribution, as well as the propulsion autocorrelation function, which defines the effective persistence time.