The equilibrium spacing will occur when the bond energy (Fn) is a minimum. This is when the net forces between the two atoms is zero:聽Fn=Fa+Fr=0.
Where:
贵补听= attractive force.
Fr聽= repulsive force.
The force between atoms,聽F, is given as:
飞丑别谤别听U聽= bond energy and聽r聽= atomic separation.
Bond stiffness, S, is given by:
飞丑别谤别听U聽= bond energy and聽r聽= atomic separation.
When the stretching is small,聽S聽is constant and therefore the bond is linear-elastic. This means that as the interatomic distance increases, the force required increases linearly.
The shape of these curves changes for different bond types and materials. A number of material properties are influenced by this curve shape. The聽F听惫蝉.听谤听curve for a flexible material will be shallower than one for a stiff material, at聽ro.