  We theoretically showed that the spontaneous polarization in ferroelectric
(FE) nanowires (NWs) can be considerably enhanced due to the nanosize
confinement by the first-principles calculations. The spontaneous polarization
along the wire direction in a fully-relaxed PbTiO3 NW with 1.8 nm diameter is
1.26 times higher than that of bulk counterpart. The tension induced by NW
surface curvature counteracts the near-surface depolarizing effect and
meanwhile leads to the unusual enhancement of spontaneous polarization. These
findings indicated that FE NWs can be promising in the applications of
nanodevices.
