Minimizing energy for external field

[ftft]

Hi, I have solved the Huckel hamiltonina for a carbon ring of 6 carbon atoms and now I want to place a charged particle near the ring and examine the energy versus the position of the charged particle using a simple Coulomb potential V(r), i.e the total hamiltoian is Huckel+V(r).

My question is, since I already have the solution for the first part, and since the second part is a one-particle operator, is it enough to minimize the energy for the second part only? I mean to find the minimum of the sum of the <i|V(r)|i>?

 

[DrClaude]

What you want to do is basically perturbation theory, so it will work so long as V(r) can be seen as a perturbation, i.e., when the charged particle is far enough away.