An approximation for the potential energy of a KCl molecule is U=A[(R^7/8r^8)-(1/r)],
where R=2.67*10^-10m and A=2.31*10^-28J*m.
a. Using this approximation find the radial component of the force on each atom. Express your answer in terms of the variables A, R0 and r.
b.Find the equilibrium separation.
c. Find the minimum potential energy.
d. Use r=R+x
to show F= -(7A/R^3)
so that the molecule's force constant is k=7A/R^3
The 3 pages file contain a detailed explanation how to expand teh radial potential and obtain the vibrational frequency of a diatomic molecule.