We finally test the ML-EFG model for size extensivity, because the system sizes included in the training set are between 200 and 256 atoms per unit cell, due to DFT performance considerations, while our target structures for -LPS and am-LPS are 384 and 576 atoms, respectively. Therefore, we calculated the EFG tensors using DFT for two structures of -and am-LPS each, extracted from the final 1 µs UFP simulations, and predicted the 7 Li EFG tensors for these four structures using the ML-EFG model (see Supplementary Information Figure ). The accuracy of the ! Q parameter for these four larger models is 9.2 kHz, which is below the experimentally known sensitivity of 7 Li SAE experiments, 10 kHz. Thus we can say with confidence that our model will have reasonable accuracy on the larger system sizes used in the final 1 µs UFP simulations.