Introduction . Oxide perovskites are fascinating materials with extensive applications owing to their intrinsic ferroelectric, antiferroelectric, and piezoelectric properties1. Halide perovskites are of high interest due to their impressive efficiencies in solar cells2 , 3, and attractive applications in optoelectronics, electrocatalysis, and thermoelectrics4 , 5 , 6. Our understanding of perovskites’ key properties is connected to deviations of the vibrational dy...