Figure 8.

Schematic representation of a multilayer feed-forward NN with inputs, X, nodes, n, and outputs, Y. In the usual implementation for the fitting of PESs, the NN maps a molecular geometry to the ground state, which could be similarly done for any other single state. In the case a manifold of excited states is described, one molecular input can also be mapped to a vector of different excited states, and additionally, other properties can be included. The forces are treated as derivatives of the NN potentials with respect to Cartesian coordinates.