An ab initio molecular dynamics investigation of Li_nAl_n clusters

Abstract

A systematic investigation of the ground-state geometries and stabilities of Li_nAl_n (n=1-10 and 13) clusters made by employing ab initio density-based molecular dynamics is reported. Although in the solid-state form, the 50:50 alloy takes on a B32-ordered structure, no evidence for such ordering has been seen for small clusters. Instead there is a clustering tendency of the Al atoms, and they tend to form inner clusters whose geometries are different from those of the free Al clusters. The Li and Al atoms favour a tetrahedral coordination due to the significant role of the s - p bonding of the electrons. A stability analysis based on energetics shows that the stability is enhanced in clusters where all of the Al faces have been capped by Li atoms, and this gives some remarkably interesting geometries, like the face-centred-cubic structure of Li₈Al₆.