Even though Goldschmidt tolerance things can semi-quantitatively predict structural distortion on The idea of steric hindrance in 3D perovskites, It's not clear-cut to apply to 2nd perovskites, because the layered segregated structures in 2nd perovskites enable the incorporation of more substantial organic and natural cations to the inorganic cages26,27,28,29,thirty. The https://crithitceramics.com/product/fireball/