# Force between 2 Atoms in solid state physics

1. Apr 7, 2006

### TheDestroyer

If we have a molcule of 2 atoms, and the potential energy between them is given as a funcion to the distance between them r:
U(r)=-A/(r^2)+B/(r^10)
Where A,B are constants,

How can we calculate the FORCE and ENERGY required to completelty separate them? and how can we calculate the force required to increase the distance between them from the equilibrium distance plus 5% or any specified distance?

And thanks

2. Apr 7, 2006

### Astronuc

Staff Emeritus
The energy required for 'separation' is given by the difference between the potentials at infinity (for which the 1/rn potential is zero) and at the nominal separation distance when the atoms are bound in the molecule (ro).

If one knows the potential, how does one determine a force?

See - http://hyperphysics.phy-astr.gsu.edu/HBASE/pegrav.html, particularly plate #2.

3. Apr 8, 2006

### TheDestroyer

Thanks, hope this works (Professor accept it), cuz this professor just know how to read from books, he dosn't know how to integrate dx lol, and i'm not getting same as his result!!

Thanks again