  The stability and electronic structure of a single monatomic Al wire has been
studied using the ab initio pseudopotential method. The Al wire undergoes two
structural rearrangements under compression, i.e., zigzag configurations at
angles of $140^o$ and $60^o$. The evolution of electronic structures of the Al
chain as a function of structural phase transition has been investigated. The
relationship between electronic structure and geometric stability is also
discussed. The 2p bands in the Al nanowire are shown to play a critical role in
its stability. The effects of density functionals (GGA and LDA) on cohesive
energy and bond length of Al nanostructures (dimmer, chains, and monolayers)
are also examined. The link between low dimensional 0D structure (dimmer) to
high dimensional 3D bulk Al is estimated. An example of optimized tip-suspended
finite atomic chain is presented to bridge the gap between hypothetical
infinite chains and experimental finite chains.
