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Cristiano De Michele

Publications and source records attributed to Cristiano De Michele.

24 records · Page 2Linked to original sources
arXiv2005

Dynamics in the presence of attractive patchy interactions

We report extensive monte-carlo and event-driven molecular dynamics simulations of a liquid composed by particles interacting via hard-sphere interactions complemented by four tetrahedrally coordinated short-range attractive ("sticky") spots, a model introduced several years ago by Kolafa and Nezbeda [J. Kolafa and I. Nezbeda, Mol. Phys. 161, 87 (1987)]. To access the dynamic properties of the model we introduce and implement a new event-driven molecular dynamics algorithm suited to study the evolution of hard bodies interacting, beside the repulsive hard-core, with a short-ranged inter-patch square well potential. We evaluate the thermodynamic properties of the model in deep supercooled states, where the bond network is fully developed, providing evidence of density anomalies. We show that, differing from models of spherically symmetric interacting particles, in a wide region of packing fractions the liquid can be super-cooled without encountering the gas-liquid spinodal. In particular, we suggest that there is one optimal packing fraction (not very different from the hexagonal ice packing fraction) at which the bond tetrahedral network fully develops. We find evidence of the dynamic anomalies characterizing network forming liquids. Indeed, around the optimal network packing, dynamics fasten both on increasing and decreasing the packing fraction. Finally we locate the shape of the isodiffusivity lines in the packing fraction-temperature plane and establish the shape of the dynamic arrest line in the phase diagram of the model. Results are discussed in connection to colloidal dispersions of sticky particles and gel forming proteins and their ability to form dynamically arrested states.

cond-mat.soft↗
arXiv2005

Molecular Correlation Functions for Uniaxial Ellipsoids in the Isotropic State

We perform event-driven molecular dynamics simulations of a system composed by uniaxial hard ellipsoids for different values of the aspect-ratio and packing fraction . We compare the molecular orientational-dependent structure factors previously calculated within the Percus-Yevick approximation with the numerical results. The agreement between theoretical and numerical results is rather satisfactory. We also show that, for specific orientational quantities, the molecular structure factors are sensitive to the particle shape and can be used to distinguish prolate from oblate ellipsoids. A first-order theoretical expansion around the spherical shape and a geometrical analysis of the configurations confirms and explains such an observation.

cond-mat.soft↗
arXiv2004

Scaling in soft spheres: fragility invariance on the repulsive potential softness

We address the question of the dependence of the fragility of glass forming supercooled liquids on the softness of an interacting potential by performing numerical simulation of a binary mixture of soft spheres with different power n of the interparticle repulsive potential. We show that the temperature dependence of the diffusion coefficients for various $n$ collapses onto a universal curve, supporting the unexpected view that fragility is not related to the hard core repulsion. We also find that the configurational entropy correlates with the slowing down of the dynamics for all studied n.

cond-mat.soft↗
arXiv2001

Equilibration times in numerical simulation of structural glasses: Comparing parallel tempering and conventional molecular dynamics

Generation of equilibrium configurations is the major obstacle for numerical investigation of the slow dynamics in supercooled liquid states. The parallel tempering (PT) technique, originally proposed for the numerical equilibration of discrete spin-glass model configurations, has recently been applied in the study of supercooled structural glasses. We present an investigation of the ability of parallel tempering to properly sample the liquid configuration space at different temperatures, by mapping the PT dynamics into the dynamics of the closest local potential energy minima (inherent structures). Comparing the PT equilibration process with the standard molecular dynamics equilibration process we find that the PT does not increase the speed of equilibration of the (slow) configurational degrees of freedom.

cond-mat.soft↗
arXiv1999

Viscous Flow and Jump Dynamics in Molecular Supercooled Liquids: II Rotations

The rotational dynamics of a supercooled molecular liquid is investigated by a molecular-dynamics numerical study. We detect rotational jumps with a waiting-time distribution which is well fitted by a truncated power law. At lower temperatures the rotational correlation times are decoupled from the viscosity.

cond-mat.stat-mech↗