Estudo de sistemas clássicos quasi-unidimensionais confinados

Abstract

We study, in this work, two mesoscopic classical quasi-unidimensional systems un- der an external parabolic con¯nement potential. In the ¯rst, which is the main part of their thesis, we analyze the structural and the dynamical properties of a binary system of charged particles, which interact with each other through a repulsive screened Coulomb potential. The ground state energies are calculated analytically and numerically. Depending on the density and on the ration (®) between the charges of the types of particle the system crystalizes in a certain number of chains. We carefully study how the ground state con¯guration changes as the density is increased (for di®erent values of ®). Numerical molecular dynamics simulation are also used as a complementary technique. In general, we show the di®erent types of particles become segregated as the density increases. Such a separation of charges leads the system to a symmetrical or to asymmetrical state. Continuous as discontinuous structural transition are found, and the order of such transitions depends on ® and on the density. The normal modes spectrum is analyzed for the one and two-chains cases. In the second system considered here, we show preliminary results for the structure of a classical system of particles interacting through a competitive shortrange attractive and long-range repulsive potential. The structure of the system is studied as a function of the density. We ¯nd several no-trivial and rather interesting ground state con¯gurations such as stripes, bubles and concentric rings.