Figure 2.

Global schematic representation of the ML model, including the calculation of descriptors, the embedding, and the NN. n_atoms, n_p, and n_emb are the number of atoms, the number of descriptors [see eq 6], and the dimension of the embedding, respectively. The diagram at the bottom illustrates, schematically, how reverse-mode automatic differentiation computes the forces; α is a shorthand index that runs over all descriptors for all atoms in the system. A cross-hatch fill represents full all-to-all connectivity between adjacent layers.