Add the full text or supplementary notes for the publication here using Markdown formatting.| C. De Michele Web
Add the full text or supplementary notes for the publication here using Markdown formatting.| C. De Michele Web
Add the full text or supplementary notes for the publication here using Markdown formatting.| C. De Michele Web
Add the full text or supplementary notes for the publication here using Markdown formatting.| C. De Michele Web
Attempts to use colloid science concepts to better understand the dynamic properties of concentrated or crowded protein solutions are challenging due to the fact that globular proteins generally have heterogeneous surfaces that result in anisotropic or patchy contributions to their interaction potential. This is particularly difficult when targeting non-equilibrium transitions such as glass and gel formation in concentrated protein solutions. Here we report a systematic study of the reduced z...| C. De Michele Web
Add the full text or supplementary notes for the publication here using Markdown formatting.| C. De Michele Web
| C. De Michele Web
| Publications | C. De Michele Web
Nanometer-sized clusters are often targeted due to their potential applications as nanoreactors or storage/delivery devices. One route to assemble and stabilize finite structures consists in imparting directional bonding patterns between the nanoparticles. When only a portion of the particle surface is able to form an inter-particle bond, finite-size aggregates such as micelles and vesicles may form. Building on this approach, we combine particle shape anisotropy with the directionality of th...| C. De Michele Web
| C. De Michele Web
For generating an isobaric–isothermal ensemble in molecular dynamics simulations of atomic systems a correct ensemble distribution can be obtained by the approach of Martyna, Tobias and Klein [J. Chem. Phys. 101, 4177–4189 (1994)]. The constituting equations of the latter approach have been also generalised to molecular systems [M. E. Tuckerman, Statistical Mechanics: Theory and Molecular Simulation, Oxford Graduate Texts (2010)] using the molecular virial instead of the atomic one. An is...| C. De Michele Web
Hydrogen hydrates are among the basic constituents of our solar system’s outer planets, some of their moons, as well Neptune-like exo-planets. The details of their high-pressure phases and their thermodynamic conditions of formation and stability are fundamental information for establishing the presence of hydrogen hydrates in the interior of those celestial bodies, for example, against the presence of the pure components (water ice and molecular hydrogen). Here, we report a synthesis path ...| C. De Michele Web
Aiming to provide a very accurate, efficient, and robust quartic equation solver for physical applications, we have proposed an algorithm that builds on the previous works of P. Strobach and S. L. Shmakov. It is based on the decomposition of the quartic polynomial into two quadratics, whose coefficients are first accurately estimated by handling carefully numerical errors and afterward refined through the use of the Newton-Raphson method. Our algorithm is very accurate in comparison with othe...| C. De Michele Web
The rotational dynamics of a supercooled model liquid of rigid [formula presented] dumbbells interacting via a Lennard-Jones potential is investigated along one single isobar. The time-temperature superposition principle, one key prediction of mode-coupling theory (MCT), was studied for the orientational correlation functions [formula presented] In agreement with previous studies we found that the scaling of [formula presented] in a narrow region at long times is better at high-[formula prese...| C. De Michele Web
Stacking Interactions and Flexibility of Human Telomeric Multimers| C. De Michele Web
The rich and complex phase diagram typical of anisotropic biological or synthetic nanoparticles, has brought a great deal of interest over the equilibrium phase behaviour of non-spherical colloids. Amongst the class of anisotropic nanoparticles, hard spherocylindrical colloids have been, over the years, extensively studied because of their optical properties, for their rich phase diagrams, and their important industrial applications, as model particles for biological systems (viruses), or for...| C. De Michele Web
Transport signatures of fragile glass dynamics in the melting of the two-dimensional vortex lattice| C. De Michele Web
We present a correction and an improvement to Algorithm 1010 [ A. Orellana and C. De Michele 2020 ]| C. De Michele Web
An anisotropic colloidal shape in combination with an externally tunable interaction potential results in a plethora of self-assembled structures with potential applications toward the fabrication of smart materials. Here we present our investigation on the influence of an external magnetic field on the self-assembly of hematite-silica core--shell prolate colloids for two aspect ratios ρ = 2.9 and 3.69. Our study shows a rather counterintuitive but interesting phenomenon, where prolate collo...| C. De Michele Web
Abstract Double-stranded DNA (dsDNA) fragments exhibit noncovalent attractive interactions between their tips. It is still unclear how DNA liquid crystal self-assembly is affected by such blunt-end attractions. It is demonstrated that stiff dsDNA fragments with moderate aspect ratio can specifically self-assemble in concentrated aqueous solutions into different types of smectic mesophases on the basis of selectively screening of blunt-end DNA stacking interactions. To this end, this type of a...| C. De Michele Web
Biological liquid crystals, originating from the self-assembly of biological filamentous colloids, such as cellulose and amyloid fibrils, show a complex lyotropic behaviour that is extremely difficult to predict and characterize. Here we analyse the liquid crystalline phases of amyloid fibrils, and sulfated and carboxylated cellulose nanocrystals and measure their Frank-Oseen elastic constants K1, K2 and K3 by four different approaches. The first two approaches are based on the benchmark of t...| C. De Michele Web
Amyloid fibrils offer the possibility of controlling their contour length, aspect ratio, and length distribution, without affecting other structural parameters. Here we show that a fine control in the contour length distribution of β-lactoglobulin amyloid fibrils, achieved by mechanical shear stresses of different levels, translates into the organization of tactoids of different shapes and morphologies. While longer fibrils lead to highly elongated nematic tactoids in an isotropic continuous...| C. De Michele Web
Abstract.: Liquid-crystalline phases in all-DNA systems have been extensively studied in the past and although nematic, cholesteric and columnar mesophases have been observed, the smectic phase remained elusive. Recently, it has been found evidence of a smectic-A ordering in an all-DNA system, where the constituent particles, which are gapped DNA duplexes, resemble chain-sticks. It has been argued that in the smectic-A phase these DNA chain-sticks should be folded as a means to suppress aggre...| C. De Michele Web
Concentrated solutions of short blunt-ended DNA duplexes at room temperature can form liquid crystal phases due to stacking interactions between duplex terminals which induce the aggregation of the duplexes into semi-flexible linear chains. Mesophases observed in these systems include nematic, columnar and cholesteric ones. This experimental system is just one of many examples, where liquid crystals ordering emerges as a result of molecular self-assembly into linear chains. In the attempt to ...| C. De Michele Web
Chromonics are a class of liquid crystals made of aqueous solutions of plank-like molecules, which self-assemble into semiflexible chains. At a given temperature a nematic phase is formed when the system reaches a sufficiently high concentration. Among the unusual properties of chromonic liquid crystals, particularly prominent is the large anisotropy of elastic constants, which leads to new phenomenologies in confined volumes. To gain insights into the microscopic origin of this behavior, we ...| C. De Michele Web
Autocatalysis, i.e., the speeding up of a reaction through the very same molecule which is produced, is common in chemistry, biophysics, and material science. Rate-equation-based approaches are often used to model the time dependence of products, but the key physical mechanisms behind the reaction cannot be properly recognized. Here, we develop a patchy particle model inspired by a bicomponent reactive mixture and endowed with adjustable autocatalytic ability. Such a coarse-grained model capt...| C. De Michele Web
Abstract.: Anisotropic interactions can bring about the formation, through self-assembly, of semi-flexible chains, which in turn can give rise to nematic phases for suitable temperatures and concentrations. A minimalist model constituted of hard cylinders decorated with attractive sites has been already extensively studied numerically. Simulation data shows that a theoretical approach recently proposed is able to properly capture the physical properties of these self-assembly-driven liquid cr...| C. De Michele Web
Abstract.: The hard cylinder model decorated with attractive patches proved to be very useful recently in studying physical properties of several colloidal systems. Phase diagram, elastic constants and cholesteric properties obtained from computer simulations based on a simple hard cylinder model have been all successfully and quantitatively compared to experimental results. Key to these simulations is an efficient algorithm to check the overlap between hard cylinders. Here, we propose two al...| C. De Michele Web
Many natural and industrial processes rely on constrained transport, such as proteins moving through cells, particles confined in nanocomposite materials or gels, individuals in highly dense collectives and vehicular traffic conditions. These are examples of motion through crowded environments, in which the host matrix may retain some glass-like dynamics. Here we investigate constrained transport in a colloidal model system, in which dilute small spheres move in a slowly rearranging, glassy m...| C. De Michele Web
Unveiling the subtle rules that control the buildup of macroscopic chirality starting from chiral molecular elements is a challenge for theory and computations. In this context, a remarkable phenomenon is the formation of helically twisted nematic (cholesteric) phases, with pitch in the micrometer range, driven by self-assembly of relatively small chiral species into supramolecular semiflexible polymers. We have developed a theoretical framework to connect the cholesteric organization to the ...| C. De Michele Web
In this paper we introduce a fully flexible coarse-grained model of immunoglobulin G (IgG) antibodies parametrized directly on cryo-EM data and simulate the binding dynamics of many IgGs to antigens adsorbed on a surface at increasing densities. Moreover, we work out a theoretical model that allows to explain all the features observed in the simulations. Our combined computational and theoretical framework is in excellent agreement with surface-plasmon resonance data and allows us to establis...| C. De Michele Web
Smectic ordering in aqueous solutions of monodisperse stiff double-stranded DNA fragments is known not to occur, despite the fact that these systems exhibit both chiral nematic and columnar mesophases. Here, we show, unambiguously, that a smectic-A type of phase is formed by increasing the DNA's flexibility through the introduction of an unpaired single-stranded DNA spacer in the middle of each duplex. This is unusual for a lyotropic system, where flexibility typically destabilizes the smecti...| C. De Michele Web
We present a general approach based on nonequilibrium thermodynamics for bridging the gap between a well-defined microscopic model and the macroscopic rheology of particle-stabilised interfaces. Our approach is illustrated by starting with a microscopic model of hard ellipsoids confined to a planar surface, which is intended to simply represent a particle-stabilised fluid-fluid interface. More complex microscopic models can be readily handled using the methods outlined in this paper. From the...| C. De Michele Web
Abstract: We put forward a theoretical framework to calculate pair distribution functions in the nematic liquid crystals formed by sphere-cylinders that self-assemble in linear chain structures. For a nematically ordered system, one can distinguish between the spatial correlations in the plane perpendicular to the crystalline axis, and in the direction parallel to the latter. Following this separation, we show that the RDFs in the parallel case can be described using a superposition of a chai...| C. De Michele Web
In particulate systems with short-range interactions, such as granular matter or simple fluids, local structure determines the macroscopic physical properties. We analyse local structure metrics derived from the Voronoi diagram of oblate ellipsoids, for various aspect ratios and global packing fractions φg. We focus on jammed static configurations of frictional ellipsoids, obtained by tomographic imaging and by discrete element method simulations. The rescaled distribution of local packing f...| C. De Michele Web
Short cylinder-like DNA duplexes, comprising 6 to 20 base pairs, self-assemble into semi-flexible chains, due to coaxial stacking interactions between their blunt ends. The mutual alignment of these chains gives rise to macroscopically orientationally ordered liquid crystal phases. Interestingly, experiments show that the isotropic-nematic phase boundary is sequence-dependent. We perform all-atom simulations of several sequences to gain insights into the structural properties of the duplex an...| C. De Michele Web
The globular protein γB-crystallin exhibits a complex phase behavior, where liquid-liquid phase separation characterized by a critical volume fraction øc = 0.154 and a critical temperature Tc = 291.8 K coexists with dynamical arrest on all length scales at volume fractions around ø ≈ 0.3-0.35, and an arrest line that extends well into the unstable region below the spinodal. However, although the static properties such as the osmotic compressibility and the static correlation length are i...| C. De Michele Web
Hard helices can be regarded as a paradigmatic elementary model for a number of natural and synthetic soft matter systems, all featuring the helix as their basic structural unit, from natural polynucleotides and polypeptides to synthetic helical polymers, and from bacterial flagella to colloidal helices. Here we present an extensive investigation of the phase diagram of hard helices using a variety of methods. Isobaric Monte Carlo numerical simulations are used to trace the phase diagram; on ...| C. De Michele Web
The anisotropy of attractive interactions between particles can favor, through a self-assembly process, the formation of linear semi-flexible chains. In the appropriate temperatures and concentration ranges, the growing aspect ratio of the aggregates can induce formation of a nematic phase, as recently experimentally observed in several biologically relevant systems. We present here a numerical study of the isotropic-nematic phase boundary for a model of bifunctional polymerizing hard cylinde...| C. De Michele Web
Comment on "generalized localization model of relaxation in glass-forming liquids"| C. De Michele Web
In the real world, diffusion-limited reactions in chemistry and biology mostly occur in crowded environments, such as macromolecular complex formation in the cell. Despite the paramount importance of such phenomena, theoretical approaches still mainly rely on the Smoluchowski theory, only valid in the infinite dilution limit. In this paper we introduce a novel theoretical framework to describe the encounter rate and the stationary density profiles for encounters between an immobilized target ...| C. De Michele Web
We put forward a theoretical approach to analyse the structure factors obtained experimentally for solutions of self-assembling anisotropic particles. This method is applicable for any system of particles forming chains in thermodynamic equilibrium and is based on studying the behaviour of the centre-centre structure factor first peak. In order to calculate the structure factor analytically, we first derive the radial distribution function. For that we use the combination of the density funct...| C. De Michele Web
We investigate numerically pseudo-first-order irreversible bimolecular reactions of the type A + B → B between hard spheres undergoing event-driven Brownian dynamics. We study the encounter rate and the survival probability of A particles as functions of the packing fraction φ in the trapping (a single particle diffusing among static non-overlapping traps) and target (many traps diffusing in the presence of a single static target particle) settings, as well as in the case of diffusing trap...| C. De Michele Web
The universal scaling between the average slow relaxation/transport and the average picosecond rattling motion inside the cage of the first neighbors has been evidenced in a variety of numerical simulations and experiments. Here, we first show that the scaling does not need information concerning the arbitrarily-defined glass transition region and relies on a single characteristic length scale a21/2 which is determined even far from that region. This prompts the definition of a novel reduced ...| C. De Michele Web
One distinctive feature of the disordered systems is the breadth of their dynamics. It includes picosecond vibrations up to processes, involving the rearrangement of the nanostructure or the diffusive transport, which become observable only over extremely long times, i.e. even weeks or years. Numerical simulations and experiments evidence unexpected strong correlations between the picosecond and the ultra-slow dynamics for a wide class of disordered systems. Here we show that the fast wigglin...| C. De Michele Web
Concentrated solutions of short blunt-ended DNA duplexes, as short as 6 base pairs, are known to order into the nematic liquid crystal phases. This self-assembly is due to the stacking interactions between duplex terminals that promotes their aggregation into polydisperse chains with a significant persistence length. Experiments show that liquid crystal phases form above a critical volume fraction depending on the duplex length. We introduce and investigate via numerical simulations, a coarse...| C. De Michele Web
Short blunt-ended DNA duplexes comprising 6 to 20 base pairs self-assemble into polydisperse semi-flexible chains due to hydrophobic stacking interactions between terminal base pairs. Above a critical concentration, which depends on temperature and duplex length, such chains order into liquid crystal phases. Here, we investigate the self-assembly of such double-helical duplexes with a combined numerical and theoretical approach. We simulate the bulk system employing the coarse-grained DNA mod...| C. De Michele Web
In the diffusion model of chemical reactions, the encounter (reaction) rate between reactant particles is governed by the Smoluchowski equation, which is a diffusion equation in a field of forces. We consider crowded environments where the particles diffuse through a \"liquid\" of like particles. Assuming that the liquid-like short-range structure around the reactant gives rise to an effective (osmotic) barrier leads us to map a complicated many-body problem to a one-dimensional problem. This...| C. De Michele Web
Recently, a simple scaling argument was introduced that allows us to map, with some precautions, Brownian and Monte Carlo dynamics for spherical particles. Here, we extend the scaling to study systems that have orientational degrees of freedom and carefully asses its validity over a wide region of temperature and density. Our work allows us to devise a Brownian Monte Carlo algorithm that produces, to a good approximation, physically meaningful trajectories with a minimum programming effort, a...| C. De Michele Web
Event-driven molecular dynamics is a valuable tool in condensed and soft matter physics when particles can be modeled as hard objects or more generally if their interaction potential can be modeled in a stepwise fashion. Hard spheres model has been indeed widely used both for the computational and theoretical description of physical systems. Recently further developments of computational techniques allow simulations of hard rigid objects of generic shape. In the present paper we will present ...| C. De Michele Web
In glassy dynamics, the rattling of particles in a cage formed by their neighbors is typically limited to a length scale of the order of the particle diameter but is nevertheless strongly coupled to the overall structural arrest of the system (solidification). Furthermore, the rattling amplitude and the structural relaxation time have been recently shown to follow the same scaling form in various polymer melts and supercooled liquids. In this paper we analyze from this perspective for the fir...| C. De Michele Web
Diffusion-limited reactions are usually described within the Smoluchowski theory, which neglects interparticle interactions. We propose a simple way to incorporate excluded-volume effects building on simulations of hard sphere in the presence of a sink. For large values of the sink-to-particle size ratio Rs, the measured encounter rate is in good agreement with a simple generalization of the Smoluchowski equation at high densities. Reducing Rs, the encounter rate is substantially depressed an...| C. De Michele Web
Diffusion-limited reactions are commonly found in biochemical processes such as enzyme catalysis, colloid and protein aggregation and binding between different macromolecules in cells. Usually, such reactions are modeled within the Smoluchowski framework by considering purely diffusive boundary problems. However, inertial effects are not always negligible in real biological or physical media on typical observation time frames. This is all the more so for non-bulk phenomena involving physical ...| C. De Michele Web
The analysis of realistic numerical simulations of a gel-forming irreversible aggregation process provides information on the role of cluster diffusion in controlling the late stages of the aggregation kinetics. Interestingly, the crossover from chemically controlled to diffusion-controlled aggregation takes place well beyond percolation, after most of the particles have aggregated in the spanning network and only small clusters remain in the sol. The simulation data are scrutinized to gain i...| C. De Michele Web
Several physical systems in condensed matter have been modeled approximating their constituent particles as hard objects. The hard spheres model has been indeed one of the cornerstones of the computational and theoretical description in condensed matter. The next level of description is to consider particles as rigid objects of generic shape, which would enrich the possible phenomenology enormously. This kind of modeling will prove to be interesting in all those situations in which steric eff...| C. De Michele Web
We study, via Brownian dynamics simulation, the kinetics of formation of branched loop-less structures for a mixture of particles with functionalities of two and three, the three-functional ones providing the branching points in the resulting network. We show that for this system, by combining the appropriate Smoluchowski rate equations, including condensation and fragmentation terms, with the thermodynamic perturbation theory of Wertheim, it is possible to provide a parameter-free descriptio...| C. De Michele Web
We report molecular dynamics simulations of a gel-forming mixture of ellipsoidal patchy particles with different functionality. We show that in this model, which disfavors the formation of bond-loops, elapsed time during irreversible aggregation-leading to the formation of an extended network-can be formally correlated with equilibrium temperature in reversible aggregation. We also show that it is possible to develop a parameterfree description of the self-assembly kinetics, bringing reversib...| C. De Michele Web
On approaching the glass transition, the microscopic kinetic unit spends increasing time rattling in the cage of the first neighbors, whereas its average escape time, the structural relaxation time τα, increases from a few picoseconds up to thousands of seconds. A thorough study of the correlation between τα and the rattling amplitude, expressed by the Debye-Waller factor, was carried out. Molecular-dynamics simulations of both a model polymer system and a binary mixture were performed by...| C. De Michele Web
We report event-driven molecular dynamics simulations of the irreversible gelation of hard ellipsoids of revolution containing several associating groups, characterizing how the cluster size distribution evolves as a function of the extent of reaction, both below and above the gel point. We find that over a very large interval of values of the extent of reaction, parameter-free mean-field predictions are extremely accurate, providing evidence that in this model the Ginzburg zone near the gel ...| C. De Michele Web
We introduce a novel algorithm to perform event-driven simulations of hard rigid bodies of arbitrary shape, that relies on the evaluation of the geometric distance. In the case of a monodisperse system of uniaxial hard ellipsoids, we perform molecular dynamics simulations varying the aspect-ratio X0 and the packing fraction . We evaluate the translational Dtrans and the rotational Drot diffusion coefficient and the associated isodiffusivity lines in the -X0 plane. We observe a decoupling of t...| C. De Michele Web
We investigate the kinetics of self-assembly by means of Brownian dynamics simulation based on a idealized fluid model (two 'sticky' spots on a sphere) in which the particles are known to form into dynamic polymer chains at equilibrium. To illustrate the slow evolution of the properties of these self-assembling fluids to their equilibrium assembled state values at long times, we perform Brownian dynamics simulations over a range of quench depths from the high temperature unassembled state to ...| C. De Michele Web
The correlation between the fast cage dynamics and structural relaxation is investigated in a model polymer system. It is shown that the cage vibration amplitude, as expressed by the Debye-Waller factor, and the relaxation time collapse on a single universal curve with a simple analytic form when the temperature, the density, the chain length and the monomer-monomer interaction potential are changed. For the physical states with the same the coincidence of the mean-square displacement, the in...| C. De Michele Web
We study a system of uniaxial hard ellipsoids by molecular dynamics simulations, changing both the aspect-ratio X0 (X0 = a/b, where a is the length of the revolution axis and b is the length of the two other axes) and the packing fraction ø. We calculate the translational 〈r2(t)〉 and rotational 〈Φ2(t)〉 mean squared displacements, the translational Dtrans and the rotational Drot diffusion coefficients and the associated isodiffusivity lines in the ø- X0 plane. For the first time, we...| C. De Michele Web
Hard spheres interacting through a square well potential were simulated by using two different methods: Brownian cluster dynamics (BCD) and event driven Brownian dynamics (EDBD). The structure of the equilibrium states obtained by both methods was compared and found to be almost identical. Self-diffusion coefficients (D) were determined as a function of the interaction strength. The same values were found by using BCD or EDBD. Contrary to EDBD, BCD allows one to study the effect of bond rigid...| C. De Michele Web
If liquids, polymers, bio-materials, metals and molten salts can avoid crystallization during cooling or compression, they freeze into a microscopically disordered solid-like state, a glass. On approaching the glass transition, particles become trapped in transient cagesin which they rattle on picosecond timescalesformed by their nearest neighbours; the particles spend increasing amounts of time in their cages as the average escape time, or structural relaxation time α, increases from a few ...| C. De Michele Web
The authors report Brownian dynamics simulation of the out-of-equilibrium dynamics (aging) in a colloidal suspension composed of rigid charged disks, one possible model for Laponite, a synthetic clay deeply investigated in the last few years by means of various experimental techniques. At variance with previous numerical investigations, mainly focusing on static structure and equilibrium dynamics, the authors explore the out-of-equilibrium aging dynamics. They analyze the wave vector and wait...| C. De Michele Web
We study the dynamics of monodisperse hard ellipsoids via a new event-driven molecular dynamics algorithm as a function of volume fraction and aspect ratio X0. We evaluate the translational Dtrans and the rotational Drot diffusion coefficients and the associated isodiffusivity lines in the X0 plane. We observe a decoupling of the translational and rotational dynamics which generates an almost perpendicular crossing of the Dtrans and Drot isodiffusivity lines. While the self-intermediate scatt...| C. De Michele Web
Brownian dynamics algorithms integrate Langevin equations numerically and allow to probe long time scales in simulations. A common requirement for such algorithms is that interactions in the system should vary little during an integration time step; therefore, computational efficiency worsens as the interactions become steeper. In the extreme case of hard-body interactions, standard numerical integrators become ill defined. Several approximate schemes have been invented to handle such cases, ...| C. De Michele Web
Gel and glass transitions in short-range attractive colloidal systems| C. De Michele Web
We report a numerical investigation of the viscoelastic behavior in models for steric repulsive and short-ranged attractive colloidal suspensions, along different paths in the attraction strength vs packing fraction plane. More specifically, we study the behavior of the viscosity (and its frequency dependence) on approaching the repulsive glass, the attractive glass, and in the reentrant region where viscosity shows a nonmonotonic behavior on increasing attraction strength. On approaching the...| C. De Michele Web
We report extensive Monte Carlo and event-driven molecular dynamics simulations of a liquid composed of 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 (Kolafa, J.; Nezbeda, I. Mol. Phys. 1987, 87, 161). To access the dynamic properties of the model, we introduce and implement a new event-driven molecular dynamics algorithm suited to study the...| C. De Michele Web
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 ...| C. De Michele Web
We report extensive Monte Carlo and event-driven molecular dynamics simulations of the fluid and liquid phase of a primitive model for silica recently introduced by Ford [J. Chem. Phys. 121, 8415 (2004)]. We evaluate the isodiffusivity lines in the temperature-density plane to provide an indication of the shape of the glass transition line. Except for large densities, arrest is driven by the onset of the tetrahedral bonding pattern and the resulting dynamics is strong in Angell's classificati...| C. De Michele Web
We numerically investigate the competition between phase separation and dynamical arrest in a colloidal system interacting via a short-ranged attractive potential. Equilibrium fluid configurations are quenched at two different temperatures below the critical temperature and followed during their time evolution. At the lowest studied T, the phase-separation process is interrupted by the formation of an attractive glass in the dense phase. At the higher T, no arrest is observed and the phase-se...| C. De Michele Web
We discuss features of simple inter-particle potentials which are able to generate low-packing fraction arrested states, i.e. gels, in the absence of a macroscopic phase separation phenomenon. We suggest that the ratio between surface and bulk free energy is crucial in favoring ideal gel states. Two possible models for gels, one based on the competition of short range attraction and long range repulsions and the other on local constraints disfavoring packed local structures are discussed. © ...| C. De Michele Web
We numerically study the dependence of the dynamics on the range of interaction Δ for the short-range square well potential. We find that, for small Δ, dynamics scale exactly in the same way as thermodynamics, both for Newtonian and Brownian microscopic dynamics. For interaction ranges from a few percent down to the Baxter limit, the relative location of the attractive-glass line and the liquid-gas line does not depend on Δ. This proves that, in this class of potentials, disordered arreste...| C. De Michele Web
The definitions of kinetic and thermodynamic fragility and their interrelations were discussed. The models for the statistical properties of the potential energy landscape (PEL) were analyzed. The relation between statistical properties of the landscape and fragility was described, building on the Adam-Gibbs relation, which connects structural relaxation times to configurational entropy. Two different possibilities for generating strong behavior were discussed.| C. De Michele Web
Saddles and softness in simple model liquids| C. De Michele Web
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...| C. De Michele Web
The transport and the relaxation properties of a biatomic supercooled liquid are studied by molecular-dynamics methods. Both translational and rotational jumps are evidenced. At lower temperatures their waiting-time distributions decay as a power law at short times. The Stokes-Einstein relation (SE) breaks down at a temperature which is close to the onset of the intermittency. A precursor effect of the SE breakdown is observed as an apparent stick-slip transition. The breakdown of Debye-Stoke...| C. De Michele Web
The techniques which allow the numerical evaluation of the statistical properties of the potential energy landscape for models of simple liquids are reviewed and critically discussed. Expressions for the liquid free energy and its vibrational and configurational components are reported. Finally, a possible model for the statistical properties of the landscape, which appears to describe correctly fragile liquids in the region where equilibrium simulations are feasible, is discussed.| C. De Michele Web
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 ...| C. De Michele Web
The transport and relaxation properties of a molecular supercooled liquid on an isobar are studied by molecular dynamics. The molecule is a rigid heteronuclear biatomic system. The diffusivity is fitted over four orders of magnitude by the power law [formula presented] with [formula presented] and [formula presented] The self-part of the intermediate scattering function [formula presented] exhibits a steplike behavior at the lowest temperatures. On cooling, the increase of the related relaxat...| C. De Michele Web