We report modifications of the ferroelectric and electrocaloric properties ofBaTiO$_3$ by defects. For this purpose, we have combined \textit{abinitio}-based molecular dynamics simulations with a simple model for defects.We find that different kinds of defects modify the ferroelectric transitiontemperatures and polarization, reduce the thermal hysteresis of the transitionand are no obstacle for a large caloric response. For a locally reducedpolarization the ferroelectric transition temperature and the adiabaticresponse are slightly reduced. For polar defects an intriguing picture emerges.The transition temperature is increased by polar defects and the temperaturerange of the large caloric response is broadened. Even more remarkable, we findan inverse caloric effect in a broad temperature range.
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