Modelo de Ising antiferromagnético em um campo externo: simulação por amostragem entrópica

Abstract

In this work we study the Ising antiferromagnetic model in an external magnetic field on the square lattice using a new sampling method, called tomographic entropic sampling. The purpose of this new entropic sampling algorithm is to visit the whole configurational space to yield good estimates of the number of system configurations, . To do so, we define fundamental classes of configurations on the square lattice. These classes partition the set of accesible configurations. In this way we can be sure that all possible classes are visited during the sampling. We estimate (L) from L = 10 to 30, using _L = 2. Then we calculate the microcanonical and canonical averages of the thermodynamic quantities of interest. We use finite size scaling analysis to determine the critical line in the h T plane, and compare these results with an approximate theoretical expression derived by Müller-Hartmann and Zittartz. We also analyse the crossing Binders cumulant of the order parameter in a critical point. In addition, at three points along the critical line, we study the critical properties of the system and estimate the critical exponents related to the order parameter, _, and to the staggered susceptibility (related to the order parameter), __.