where U nb (X, X GP , A GP ) is the nonbonded interaction energy between the ghost particle atoms and the remainder of the system (X). The forces on the positions and attributes of the ghost particles are determined by the negative gradients of U. Eq. 7 makes clear that these depend both on U FT (and in turn, the loss function L) and U nb . The relative contributions of these forces to the motion of the particles and attributes is again determined by the parameter s.