Size and shape effects in ferroelectric nanoparticles

STACHIOTTI, M.G.; DI RINO, F; SEPLIARSKY, M.

Natal

Workshop; nternational Workshop on Topological Structures in Ferroic Materials; 2018

International Institute of Physics

Weapplied a first-principles-based atomistic shell model approach toinvestigate the influence of size and shape in the formation ofdifferent polar structures in nanoparticles of the ferroelectricPbTiO3.The studies were carried performing molecular dynamics simulation infreestanding nanodots of cylindrical, spherical and ellipsoidalshape. In cylinders with diameter equal to the height (D=H), theinitialordered structure corresponds to a vortex configuration with a corealong the cylinder axis. As the size increases thepolar configurations evolve to regions with nearly uniform dipoleorientation. In each region or domain, local dipoles adopt one of thefour equivalent <100> direction and rotates 90 from one domainto the other in an overall closed loop. The 90º domains walls areinitially oriented in {100} and {010}, and they are containing in{110} planes with a further size increment. The polar configurationsbecome more complex with the size, exhibiting three zones withdifferentiated characteristics as we move away from the central axis.While a similar behavior is observed in elongated cylinders (D <H),flattered ones display a sequence oftopological transformations driven by the aspect ratio D/H. Theobserved polar configurations include one- and multiple-vortexstates, bubble state, and different multi-domain structures as theaspect ratio increases. Finally, theabsence of flat surfaces of spheres and spheroids provides anadditional degree of complexity to the stability of the possiblepolar structures. We found that the spheres behaves similar to thecylinders with D=H and polar patterns of spheroids approach the onesobserved in cylinders large distortions. p { margin-bottom: 0.25cm; direction: ltr; color: rgb(0, 0, 0); line-height: 120%; text-align: left; }p.western { font-family: "Liberation Serif", serif; font-size: 12pt; }p.cjk { font-family: "Noto Sans CJK SC Regular"; font-size: 12pt; }p.ctl { font-family: "FreeSans"; font-size: 12pt; }