The switching function is applied when the maximum distance in a trimer is between 7 Å and 8 Å, and the energy contribution is 0 when the maximum internuclear distance in the trimer is beyond 8 Å. For the 4-body bases, the Morse range parameter is 1.2 bohr, and the maximum polynomial order is 7. The switching range for 4-body is between 5 Å and 6 Å. All the bases are purified, that is, any polynomial that does not go to zero when an atom is infinitely far away from the remaining atoms is removed from the bases. There are 32, 78, hydrogens. This number of terms is an order of magnitude smaller than the number of terms in the fragmented approach. However, there are many terms to evaluate. Specifically, with the above choice of hyperparameters there are about 10 4 4-b interactions (the exact number depends on the geometry, and is typically between 10,000 and 25,000). Without a cutoff there would be 135,751 4-b interactions.