Voronoi Glass-Forming Liquids : A Structural Study

We introduce a new theoretical model of simple fluid, whose interactions, defined in terms of the Voronoi cells of the configurations, are local and many-body. The resulting system is studied both theoretically and numerically. We show that the fluid, though sharing the global features of other models of fluids with soft interactions, has several unusual characteristics, which are investigated and discussed.Comment: 19 pages, 9 figure

New conserved structural fields for supercooled liquids

By considering Voronoi tessellations of the configurations of a fluid, we propose two new conserved fields, which provide structural information not fully accounted for by the usual 2-point density field fluctuations (structure factor). One of these fields is scalar and associated to the Voronoi cell volumes, whereas the other one, termed the "geometrical polarisation", is vectorial, related to the very local anisotropy of the configurations. We study the static and dynamical properties of these fields in the supercooled regime of a model glass-forming liquid. We show in particular that the geometrical polarisation is both statically correlated to the force field and contrary to it develops a plateau regime when the temperature is lowered. We attribute this behaviour to the microsopic disorder of the underlying inherent structures (IS) which dictate the dynamics on time scales larger than the true microscopic time, in the strong supercooled regime. In this respect, this work raises the issue of to what extent the inter IS dynamics, intrinsically anisotropic and collective (cf. T.B. Schr{\o}der et al. {\it J. of Chem. Phys.}, {\bf 112}, 9834 (2000)), could be related to their polarisation field.Comment: submitted to EPJE the 09/30/201

Microscopic structure of compacted polyelectrolyte complexes: Insides from molecular dynamics simulations

International audienc

Shear-strain and shear-stress fluctuations in generalized Gaussian ensemble simulations of isotropic elastic networks

International audienceShear-strain and shear-stress correlations in isotropic elastic bodies are investigated both theoretically and numerically at either imposed mean shear-stress tau (lambda - 0) or shear-strain gamma (lambda - 1) and for more general values of a dimensionless parameter. characterizing the generalized Gaussian ensemble. It allows to tune the strain fluctuations mu(gamma gamma) beta V = (1 - lambda)/G(eq) with beta being the inverse temperature, V the volume, gamma the instantaneous strain and G(eq) the equilibrium shear modulus. Focusing on spring networks in two dimensions we show, e.g., for the stress fluctuations mu(tau tau) beta V (tau being the instantaneous stress) that mu(tau tau)|(lambda) = mu A - lambda G(eq) with mu A = mu(tau tau)vertical bar(lambda= 0) being the affine shear-elasticity. For the stress autocorrelation function C-tau tau(t) beta V this result is then seen (assuming a sufficiently slow shear-stress barostat) to generalize to C-tau tau(t)|(lambda) = G(t) - lambda G(eq) with G(t) = C-tau tau(t)|(lambda= 0) being the shear-stress relaxation modulus