Molecular Dynamic Study of the Al and Fe Liquid Structure

F. SAPORITI; F. AUDEBERT; S. GABBANELLI

Workshop; Pan American Advanced Institute on Physics at the Nanometer Scale; 2003

Nanostructured and amorphous alloys have been studied in the last years because they show interesting properties for technological applications. Usually these alloys are prepared by rapid solidification process. The structure obtained depend of the cooling rate and the atomic configuration in the liquid state. It is widely recognized that empirical potential can be used together with molecular dynamics (MD) simulation to analyse the structural properties of the most metals with good accuracy. In the present work a MD simulation has been performed to study the structure of the Al and Fe mono-atomic systems at different temperatures. The embedded atom method (EAM) was used for model the potential interaction between the atoms. The motion of 1374 atoms was studied in the frame of micro-canonical ensemble. The systems of the atoms investigated occupy a cubic box with a periodic boundary condition. In the transient state the atoms are arranged in nodes of the fcc lattice. It was used a velocity according to the Maxwell distribution for a temperature higher than the melting point. After thermal stabilisation the system was cooled down in an average equivalent rate of 10E14 K/s until the desired temperature. From the recorded of the atomic positions after these thermodynamics treatments it was possible to study the structure using the radial distribution function (RDF) and the triplet correlation function f(). The RDF of the Al and the Fe systems obtained from the MD simulation are in agreement with those experimentally determined for the liquid systems reported in the literature. The Al under-cooled liquid showed a gradual splitting of the second peaks of the RDF as the temperature decreased. The RDF of the Fe for the under-cooled liquid showed that the second peak became more asymmetric as temperature decreased. The f() in both cases showed two important peaks which shifted to higher angles and became narrower with the decreasing of the temperature. The f() obtained for both mono-atomic systems are compared with the theoretical angular position for the fcc and the icosahedral local arrangements.