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Papers by chahrazed meddah

We focus on the simulation of flexible and semiflexible polymer systems using the multicanonical ... more We focus on the simulation of flexible and semiflexible polymer systems using the multicanonical Monte Carlo method where we study their thermodynamic properties and conformational behavior. First, we investigate transition signatures of flexible homopolymer chains where monomers interact through a standard Lennard-Jones potential. In the second time, we introduce a square well potential that produces helical structures. The idea behind the use of those different potentials is to construct a phase diagram where we can characterize the liquid, solid, crystalline and helical phases.

The Journal of Chemical Physics, 2016

Using molecular dynamics simulations, we study and compare the pressure, P, and the surface tensi... more Using molecular dynamics simulations, we study and compare the pressure, P, and the surface tension, γ, of linear chains and of ring polymers at the hard walls confining both melts into a slit. We examine the dependence of P and γ on the length (i.e., molecular weight) N of the macromolecules. For linear chains, we find that both pressure and surface tension are inversely proportional to the chain length, P(N)−P(N→∞)∝N−1,γ(N)−γ(N→∞)∝N−1, irrespective of whether the confining planes attract or repel the monomers. In contrast, for melts comprised of cyclic (ring) polymers, neither the pressure nor the surface tension is found to depend on molecular weight N for both kinds of wall-monomer interactions. While other structural properties as, e.g., the probability distributions of trains and loops at impenetrable walls appear quantitatively indistinguishable, we observe an amazing dissimilarity in the probability to find a chain end or a tagged monomer of a ring at a given distance from t...

We perform a comparative study of the scaling of polymer size and diffusion dynamics with changin... more We perform a comparative study of the scaling of polymer size and diffusion dynamics with changing molecular weight N for melts comprised of ring- and linear polymers in a broad interval of chain lengths, 10 ≤ N ≤ 2048 and observe a qualitative difference caused by distinct topology. Using large-scale molecular dynamics simulations of a bead-spring coarse grained model, we find that the Flory exponent for linear chains in a dense solution, νL = 1/2, varies in the case of rings from νR = 1/2 for short rings, over νR = 2/5 for rings with intermediate length, down to ν R = 1/3 for long rings 800 ≤ N ≤ 2048, confirming thus recent findings of the behavior of such long rings in a melt effectively as compact globules. In our studies of ring dynamics we allow for the hydrodynamic interactions in the system by using Dissipative Particle Dynamics (DPD) and find that cyclic polymers (rings) diffuse faster than linear chains with the same molecular weight owing to the absence of chain ends tha...

EPJ Web of Conferences, 2013

We focus on the simulation of flexible and semiflexible polymer systems using the multicanonical ... more We focus on the simulation of flexible and semiflexible polymer systems using the multicanonical Monte Carlo method where we study their thermodynamic properties and conformational behavior. First, we investigate transition signatures of flexible homopolymer chains where monomers interact through a standard Lennard-Jones potential. In the second time, we introduce a square well potential that produces helical structures. The idea behind the use of those different potentials is to construct a phase diagram where we can characterize the liquid, solid, crystalline and helical phases.

The Journal of Chemical Physics, 2016

Using molecular dynamics simulations, we study and compare the pressure, P, and the surface tensi... more Using molecular dynamics simulations, we study and compare the pressure, P, and the surface tension, γ, of linear chains and of ring polymers at the hard walls confining both melts into a slit. We examine the dependence of P and γ on the length (i.e., molecular weight) N of the macromolecules. For linear chains, we find that both pressure and surface tension are inversely proportional to the chain length, P(N)−P(N→∞)∝N−1,γ(N)−γ(N→∞)∝N−1, irrespective of whether the confining planes attract or repel the monomers. In contrast, for melts comprised of cyclic (ring) polymers, neither the pressure nor the surface tension is found to depend on molecular weight N for both kinds of wall-monomer interactions. While other structural properties as, e.g., the probability distributions of trains and loops at impenetrable walls appear quantitatively indistinguishable, we observe an amazing dissimilarity in the probability to find a chain end or a tagged monomer of a ring at a given distance from t...

We perform a comparative study of the scaling of polymer size and diffusion dynamics with changin... more We perform a comparative study of the scaling of polymer size and diffusion dynamics with changing molecular weight N for melts comprised of ring- and linear polymers in a broad interval of chain lengths, 10 ≤ N ≤ 2048 and observe a qualitative difference caused by distinct topology. Using large-scale molecular dynamics simulations of a bead-spring coarse grained model, we find that the Flory exponent for linear chains in a dense solution, νL = 1/2, varies in the case of rings from νR = 1/2 for short rings, over νR = 2/5 for rings with intermediate length, down to ν R = 1/3 for long rings 800 ≤ N ≤ 2048, confirming thus recent findings of the behavior of such long rings in a melt effectively as compact globules. In our studies of ring dynamics we allow for the hydrodynamic interactions in the system by using Dissipative Particle Dynamics (DPD) and find that cyclic polymers (rings) diffuse faster than linear chains with the same molecular weight owing to the absence of chain ends tha...

EPJ Web of Conferences, 2013