The potential energy of a diatomic molecule (a two-atom system like H₂ or O₂) is given by
U = A/r¹² - B/r⁶
where r is the separation of the two atoms of the molecule and A and B are positive constants. This potential energy is associated with the force that binds the two atoms together.
is the force repulsive (the atoms are pushed apart) or attractive (they are pulled together) if their separation is smaller than the equilibrium separation?