Subject: ZINDO method related questions

From: Lorant Janosi <lj8q5(at)mizzou.edu>
Date: Tue, 18 Nov 2003 15:43:59 -0600

Using g98 revision A11:
I used ZINDO method to compute the excited states for a chlorophyll
molecule. Everything worked just fine.
But when I included point charges around it, everything went totally
wrong. No SCF convergence or, if I removed some of the point charges,
there was an SCF convergence but the excited levels were completely
wrong and unreal.
My questions are:
1) Why is this happening?
2) How can it be fixed? (using ZINDO of course)
3) How is the Hamiltonian computed when point charges are included?
4) Why is ZINDO so sensitive (even to symmetry)?

Using g03:
All results computed with ZINDO for the chlorophyll molecule are
exactly the same with or without point charges included. It's like
they are completely ignored by g03.
My questions are:
1) Can anyone explain that to me?
2) Why is this happening?
3) Is it possible at all to use ZINDO and include point charges in the
system?

Thank you.
Lori.