  The authors apply first-principles calculations to investigate the interplay
between structural, electronic, and magnetic properties of nanostructures
composed of narrow nanotubes filled with metallic nanowires. The focus is on
the structural and magnetic responses of Ni-filled nanotubes upon radial
compression. Interestingly, metastable flattened structures are identified, in
which radially deformed nanotubes are stabilized by the interactions with the
encapsulated wire. Moreover, our results indicate a quenching of the magnetic
moment of the wire upon compression, as a result of the transfer of charge from
the $s$ to the $d$ orbitals of the atoms in the wire.
