Atomic Ordering at the Interfaces Between Liquid Aluminum and Polar AlN{0 0 0 1} Substrates

Abstract

AlN particles are formed in liquid Al metals/alloys during liquid-dealing and casting. They may act as potential nucleation sites during solidification. Along its [0 0 0 1] axis, AlN consists of Al3+N3- dipolar double-atom layers in the ionic model. Thus, the AlN{0 0 0 1} substrates are terminated by either an Al3+ or a N3- layer, being polar. Here we investigate the atomic ordering at the interfaces between liquid-aluminum and AlN{0 0 0 1} using an ab initio molecular dynamics technique. We have observed a rich variety of interfacial chemistry and identified an ordered Al layer terminating the substrates. The newly formed terminating Al atoms are positively charged. The liquid Al adjacent to the interfaces exhibit strong layering but weak in-plane ordering. The obtained information helps get insight into the role of aluminum nitride as potential nucleation sites in solidification of Al-metals, and further enriches our knowledge about nucleation