Direct and indirect methods based on effective Hamilton for electrocaloric effect of BaTiO₃ nanoparticle

Low dimensional ferroelectric materials, including nano thin films, nanowires and nanoparticules, exhibit excellent electrocaloric effect (ECE) and have potential application in solid-state cooling devices. Predicting the ECE property of nanoscale ferroelectrics is of scientific significance and practice importance. Here, the direct and indirect methods based on effective Hamilton are employed to study the ECE in BaTiO₃ nanoparticle under different electric fields and temperatures. In indirect method, the Monte Carlo simulation is used to obtain the polarization changes with temperature under different electric fields. The ECE is calculated indirectly based on the Maxwell relation. In direct method, the demon energy is introduced into the system in order to obtain the ECE directly. The results shows that the difference between the peak values of direct method and indirect method is less than 5%, which means both direct method and indirect method can be used to simulate the ECE of ferroelectric nanoparticle.