Subject: CCL:Re: Excited state optimisation with DFT

From: "Stefan Fau" <fau_at_qtp.ufl.edu>
Date: Mon, 27 Oct 2003 14:32:42 -0500

Hi Mikael,

a "ground state" method uses the variational principle to find the
best wavefunction for a given spatial and electronic symmetry.
Therefore, it can be used whenever there are no lower-lying
states of the same (nuclear and electronic) symmetry and
multiplicity.

In contrast, excited state methods find wavefunctions that are
orthogonal to all lower-lying wavefunctions of the same symmetry
and multiplicity.

The results of regular ground-state methods for symmetry-restricted
calculations should always be checked to see if there are imaginary
frequencies. Similarly, a different multiplicity may have a lower
energy
solution.

Stefan
______________________________________________________________________
Dr. Stefan Fau                    |      fau_at_qtp.ufl.edu
University of Florida             |     (352) 392-6714
Quantum Theory Project
2319 NPB #92, P.O.Box 118435
Gainesville, FL 32611-8435