# Potential energy separation curve

1. Sep 2, 2010

### cyt91

Here's my understanding of the Force /Separation graph, I'm open to
criticism/ridicule if I've got it wrong:

If the two atoms are pushed together, then there is a repulsive force between
them of a positive magnitude. If they are separated by a distance r, then the
two forces (repulsive/attractive) are equal but opposite and the atoms are in a
state of equilibrium. At a separation greater than r, the force is that of
attraction, and if the separation is greater than 2r, then the attraction
tends to zero.

Potential Energy/Separation:

If the two atoms are separated by an infinite distance, then there is no
attraction between them, and there is no Potential Energy. But as they come
closer together, Potential Energy decrease until at a distance of r, potential
energy is at a minimum. If the separation is reduced further, the line of
Potential Energy passes through zero.

Why is the potential energy zero? What actually happens to the 2 atoms when the potential energy becomes zero?

I'm confused, can anyone clear this up for me please?

Thanks.

2. Sep 2, 2010

### nasu

Nothing special actually. The absolute value of the potential energy has no meaning as the reference point can be arbitrarily chosen , in principle.
The existence of a minimum (no matter if this value is negative, positive or even zero) is a meaningful feature and does not depend on the choice of the reference point.