Hello all , I am interested in the following problem: In an ensemble of atoms, the forces on atom A and atom B are given by the vectors Fa=Fax+Fay+Faz and Fb=Fbx+Fby+Fbz, respectively. Their respective positions are given by, Pa=Pax+Pay+Paz and Pb=Pbx+Pby+Pbz I have two questions: (1) Would I be right in thinking that the dot product of Fa and Pb will give the magnitude of the force on atom A in the direction of atom B? (2) Also, is the dot product of Fa and Fb the attractive force between the atoms? Any help would be greatly appreciated !! Ewan.