What exactly is this potential energy? I was searching and its looks like electric potential energy (U = K*Q*q/d - K*Q*q /d0), because the two atoms attract each other that means that the product of Q*q = negative, so, a negative energy. Ok, that's make sense, but why when the repulsive forces and attractive forces enter in equilibrium the energy still negative ? Does not that means the molecules keep attracting and coming closer and closer ? I already searched about it, but I cant understand this part.