• Support PF! Buy your school textbooks, materials and every day products Here!

How to graph potential energy for 2 atoms in diatomic molecule w/ 3 unknowns

  • Thread starter collin2012
  • Start date
  • #1

Homework Statement



The potential energy of two atoms in a diatomic molecule is approximated by

U(r)=a/r^12 - b/r^6,

where r is the spacing between the atoms and a and b are positive constants.

Find the force F(r) on one atom as a function of r.

Make two graphs one of U(r) versus r and one of F(r) versus r.

Homework Equations



F(r) = -(dU/dr)

The Attempt at a Solution



I know F(r) = -(dU/dr).

So, F(r) = (12a/r^13) - (6b/r^7)

And then I get stuck. I don't know how to make a plot of U(r) vs r and F(r) vs r when I don't know a and b.

I want to plug values of r=[0.1, 0.2, 0.3, ...] into the F(r) equation, but I have no idea what to do about a and b.

This question has been asked before on this forum and I have looked at the hints, but I am still completely lost.

Could someone please get me pointed in the right direction.

Thanks.
 

Answers and Replies

  • #2
So I figured out that U(r) = a/r^12 - b/r^6 is a simplified version of the Lennard-Jones potential and I know what the graph looks like now, but I still don't understand how you get it. I am so lost. Could someone please explain. Thanks.
 

Related Threads on How to graph potential energy for 2 atoms in diatomic molecule w/ 3 unknowns

  • Last Post
Replies
14
Views
4K
  • Last Post
Replies
5
Views
4K
  • Last Post
Replies
8
Views
1K
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
2
Views
17K
Replies
0
Views
870
Replies
14
Views
3K
  • Last Post
Replies
2
Views
1K
Replies
12
Views
2K
Top