Microstructural analysis of the radial distribution function for liquid andamorphous Al

Abstract

Constant-pressure molecular dynamics simulations and analysisof the local atomic structures have been performed to study theconventional and ‘inherent’ structural evolution of liquid Al during rapidsolidification. The results show that the radial distribution functionsg(r)exhibit a second-peak splitting feature not only for the general structures of theamorphous states but also for the inherent structure of liquid states. The second peakof g(r)decomposes into three main components, each corresponding to different pairs.The first subpeak in the inherent structure of the liquid arises from 2211 and 2331pairs (which correspond to triangles with a common side and the tetrahedrasharing a face respectively), while the first subpeak in the amorphous state arisesfrom 2331 pairs; in both cases the second subpeak is due to the 2101 pairs (lineartrimers). The existence of a shoulder or the splitting in the second peak ofg(r)in the amorphous state, and even in the undercooled liquid state, results mainlyfrom the increase in number of and aggregation of the tetrahedra, which in turngive rise to the presence of entities with local icosahedral order.