Where M is the number of conformations in the data set D, N m the number of atoms in each conformation, θ is the full vector of parameters of the model, r i , Z i , . . . represents the dependence of the predicted atomic charge on the coordinates and atomic number of atom i and all atoms surrounding it within a given cutoff distance (5.2 Å for the model considered in this article), and q ref i is the corresponding reference atomic charge.