Since it is experimentally challenging to detect closely spaced aluminium atoms and their effect on the chemical shift is large, comparison of the predicted values with the experimental data has to be done with caution. To overcome this challenge, it is advisable to consider for comparison only zeolite samples with a very high Si/Al ratio. In such samples, closely spaced aluminium pairs are less common, making it easier to validate the predictions and assess their accuracy. This approach minimizes the complications associated with aluminium pair interactions and provides a clearer comparison between predicted and experimental chemical shift values.