There are multiple methods to calculate chemical shielding, each varying in accuracy and computational cost. The most computationally intensive approach involves using ab initio methods, such as DFT, to calculate the chemical shielding values. Despite its high accuracy, the substantial computational cost makes it impractical for large numbers of structures, e.g., as is needed to properly account for dynamical effects. The simplest approach proposed by Lippmaa et al. predicts directly the Al NMR chemical shift δ (Al), i.e., circumventing the calculation of the chemical shielding altogether, and approximates δ (Al) as a function of the average T-O-T angle α(T-O-T), as described by the following equation: