  Using the Landau-Ginzburg-Devonshire approach, we study stress-induced
transformations of polarization switching in ferrielectric CuInP2S6
nanoparticles for three different shapes: a disk, a sphere, and a needle.
Semiconducting properties of a nanoparticle are modeled by a surface charge
layer, whose effective screening length can be rather small due to the
field-effect. We reveal a very strong and unusual influence of hydrostatic
pressure on the appearance of polarization switching in CuInP2S6 nanoparticles,
hysteresis loops shape, magnitude of the remanent polarization, and coercive
fields, and explain the effects by the anomalous temperature dependence and
"inverted" signs of CuInP2S6 linear and nonlinear electrostriction coupling
coefficients. In particular, by varying the sign of the applied pressure (from
tension to compression) and its magnitude (from zero to several hundreds of
MPa), quasi-static hysteresis-less paraelectric curves can transform into
double, triple, pinched, or single hysteresis loops. Due to the sufficiently
wide temperature and pressure ranges of double, triple, and pinched hysteresis
loop stability (at least in comparison with many other ferroelectrics),
CuInP2S6 nanodisks can be of particular interest for applications in energy
storage (in the region of double loops), CuInP2S6 nanospheres maybe suitable
for dynamic random access multibit memory, and CuInP2S6 nanoneedles are
promising for non-volatile multibit memory cells (in the regions of triple and
pinched loops). The stress control of the polarization switching scenario
allows the creation of advanced piezo-sensors based on CuInP2S6 nanocomposites.
