Laboratoire de Physique Théorique et Modèles Statistiques

Soutenance de thèse : Carlos Eduardo Alvarez Cabrera

On Shape abd Electrostatics: Statistical Mechanics Studies of Model Systems

Carlos Eduardo Alvarez Cabrera

This doctoral work presents a series of studies of systems in which the particles interact by means of spheroidal hard core and electrostatic interactions. We first consider a dipolar hard sphere bilayer, studied by means of Monte Carlo (MC) simulations. The pressure between the layers is found to vary as -1/h⁵, where h is the distance between layers. We observed vortex like structures, frustrated by the finite size of the system.
Next we obtained the analytical solution to the screened potential of charged spheroidal colloid particles in the Debye-Huckel regime for Neumann and Dirichlet boundary conditions. This latter result agrees with the solution of the Poisson-Boltzmann equation far from the colloid for strongly charged particles. We also perform MC simulations of spheroidal colloids with a point charge at the center and find, both analytically and in simulations, that the effective potential is stronger in the direction where the curvature of the colloid is higher.
Finally we present two studies under progress. The first one deals with the effect of the addition of small spheres to spheroidal prolate particles in the nematic phase. We have seen that for an aspect ratio of 3 this effect is mild, but for an aspect ratio of 4, the nematic to isotropic transition is shifted to higher spheroid densities. In the second work, preliminary MC results for a size bidisperse spherical charged colloidal system are provided. This allows for a test of recently proposed mean-field approaches for polydisperse charged systems (cell model and renormalized jellium). In addition, we have found that as the size difference between the colloids is increased, the screening of the smaller species increases, while the opposite effect is observed for the larger species.

Vendredi 25 juin à 10h30

LPTMS-batiment 100, salle des conseils, Orsay


Calendrier des séminaires

Mai
Juillet
Juin 2010
lun. mar. mer. jeu. ven.
 
1
16:00» Seminaire LPTMS: Uzy Smilansky (Weizmann)
2
3
14:00» Séminaire commun LPT-LPTMS : Petr Sulc
4
11:00» Séminaire du LPTMS : Yoshiyuki Kabashima
7
14:00» Séminaire PHYSTAT-SUD : Jon Keating
8
11:00» Seminaire LPTMS : Luigi Cantini (LPT ENS)
9
10
11
14
15
11:00» Seminaire LPTMS: Rhoda Hawkins
16
17
18
14:00» Séminaire Physique Biologique et Systèmes Complexes : Guillaume Romet-Lemonne
21
22
11:00» Semianire LPTMS: Martin Lenz (Chicago)
23
24
16:00» Séminaire du LPTMS : Gunnar Boldhaus
25
10:30» Soutenance de thèse : Carlos Eduardo Alvarez Cabrera
15:00» Séminaire exceptionnel du LPTMS : Paolo Solinas
28
29
11:00» Seminaire LPTMS: Celine Nadal, Alvaro Rojo
30