Abstract: The results of a systematic study of octahedral tilting in oxo- and fluoroperovskites by density functional theory (DFT) calculations are presented and discussed. Eleven perovskites displaying different structural, magnetic, and metallic properties have been studied by means of nine exchange-correlation functionals, ranging from the basic local density approximation to more advanced hybrid functionals, in order to determine the accuracy of these methods for the prediction of octahedral rotation angles. Octahedral tilting has attracted much attention lately due to the possibility of using them to trigger improper ferroelectricity and new families of multiferroic materials. We show that all DFT methods tend to overestimate the octahedral rotation angles by approximately 20 %, with this quantity being only slightly corrected by hybrids, including, at least, 25% of the Hartree?Fock exchange. We propose a correction to the prediction of these angles based on quantum fluctuations and the anharmonic nature of the energy surface around the minimum but find that it is only important for very small rotation angles appearing in systems like SrTiO3.

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