3,081 research outputs found
Liquid stability in a model for ortho-terphenyl
We report an extensive study of the phase diagram of a simple model for
ortho-terphenyl, focusing on the limits of stability of the liquid state.
Reported data extend previous studies of the same model to both lower and
higher densities and to higher temperatures. We estimate the location of the
homogeneous liquid-gas nucleation line and of the spinodal locus. Within the
potential energy landscape formalism, we calculate the distributions of depth,
number, and shape of the potential energy minima and show that the statistical
properties of the landscape are consistent with a Gaussian distribution of
minima over a wide range of volumes. We report the volume dependence of the
parameters entering in the Gaussian distribution (amplitude, average energy,
variance). We finally evaluate the locus where the configurational entropy
vanishes, the so-called Kauzmann line, and discuss the relative location of the
spinodal and Kauzmann loci.Comment: RevTeX 4, 8 pages, 8 eps figure
Aging in short-ranged attractive colloids: A numerical study
We study the aging dynamics in a model for dense simple liquids, in which
particles interact through a hard-core repulsion complemented by a short-ranged
attractive potential, of the kind found in colloidal suspensions. In this
system, at large packing fractions, kinetically arrested disordered states can
be created both on cooling (attractive glass) and on heating (repulsive glass).
The possibility of having two distinct glasses, at the same packing fraction,
with two different dynamics offers the unique possibility of comparing --
within the same model -- the differences in aging dynamics. We find that, while
the aging dynamics of the repulsive glass is similar to the one observed in
atomic and molecular systems, the aging dynamics of the attractive glass shows
novel unexpected features.Comment: 8 pages, 11 figures, submited to Journal of Chemical Physic
Mode-Coupling Theory of Colloids with Short-range Attractions
Within the framework of the mode-coupling theory of super-cooled liquids, we
investigate new phenomena in colloidal systems on approach to their glass
transitions. When the inter-particle potential contains an attractive part,
besides the usual repulsive hard core, two intersecting liquid-glass transition
lines appear, one of which extends to low densities, while the other one, at
high densities, shows a re-entrant behaviour. In the glassy region a new type
of transition appears between two different types of glasses. The complex
phenomenology can be described in terms of higher order glass transition
singularities. The various glass phases are characterised by means of their
viscoelastic properties. The glass driven by attractions has been associated to
particle gels, and the other glass is the well known repulsive colloidal glass.
These correspondences, in associations with the new predictions of glassy
behaviour mean that such phenomena may be expected in colloidal systems with,
for example, strong depletion or other short-ranged attractive potentials.Comment: 17 pages, 8 figure
Theoretical and numerical study of the phase diagram of patchy colloids: ordered and disordered patch arrangements
We report theoretical and numerical evaluations of the phase diagram for a
model of patchy particles. Specifically we study hard-spheres whose surface is
decorated by a small number f of identical sites ("sticky spots'') interacting
via a short-range square-well attraction. We theoretically evaluate, solving
the Wertheim theory, the location of the critical point and the gas-liquid
coexistence line for several values of f and compare them to results of Gibbs
and Grand Canonical Monte Carlo simulations. We study both ordered and
disordered arrangements of the sites on the hard-sphere surface and confirm
that patchiness has a strong effect on the phase diagram: the gas-liquid
coexistence region in the temperature-density plane is significantly reduced as
f decreases. We also theoretically evaluate the locus of specific heat maxima
and the percolation line.Comment: preprint, 32 pages, 6 figures, 3 tables, J. Chem. Phys. in pres
Phase diagram of patchy colloids: towards empty liquids
We report theoretical and numerical evaluations of the phase diagram for
patchy colloidal particles of new generation. We show that the reduction of the
number of bonded nearest neighbours offers the possibility of generating liquid
states (i.e. states with temperature lower than the liquid-gas critical
temperature) with a vanishing occupied packing fraction (), a case which
can not be realized with spherically interacting particles. Theoretical results
suggest that such reduction is accompanied by an increase of the region of
stability of the liquid phase in the (-) plane, possibly favoring the
establishment of homogeneous disordered materials at small , i.e. stable
equilibrium gels.Comment: 4 pages, 4 figures, revised version, accepted in Phys. Rev. Let
Esperienze progettuali di edifici per attivitĂ natatorie
Alla città di Milano manca un centro natatorio di spicco atto ad ospitare eventi sportivi di caratura internazionale. L’articolo affronta il tema della progettazione di edifici per attività natatorie proponendo l’inquadramento di possibili soluzioni progettuali attraverso degli studi eseguiti nell’ambito del corso “Building Technology Studio” al Politecnico di Milano. I progetti sono contestualizzati nell’ambito di un quartiere originariamente pensato per il rapporto con l’acqua, ovvero Porto di Mare, sito alla periferia sud-est di Milano
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