  We present the relation between the atomic and spin-electronic structures of
infinite single-row atomic wires made of Al atoms during their elongation using
first-principles molecular-dynamics simulations. Our study reveals that the
Peierls transition indeed occurs in the wire with magnetic ordering: it
ruptures to form a trimerized structure with antiferromagnetic ordering and
changes from a conductor to an insulator just before forming a linear wire of
equally-spaced atoms. The formation of the trimerized wire is discussed in
terms of the behavior of the $\sigma$-symmetry bands of the Al wire.
