  We investigate electronic structures of Al quantum wires, both unsupported
and supported on the (100) NaCl surface, using the density-functional theory.
We confirm that unsupported nanowires, constrained to be linear, show
magnetization when elongated beyond the equilibrium length. Allowing ions to
relax, the wires deform to zig-zag structures with lower magnetization but no
dimerization occurs. When an Al wire is deposited on the NaCl surface, a
zig-zag geometry emerges again. The magnetization changes moderately from that
for the corresponding unsupported wire. We analyse the findings using electron
band structures and simple model wires.
