CCL:G: Gaussian03 Error: Density matrix is not changing but DIIS error -
- From: Eric Breynaert <eric.breynaert,biw.kuleuven.be>
- Subject: CCL:G: Gaussian03 Error: Density matrix is not changing
but DIIS error - Suggested solutions
- Date: Tue, 28 Nov 2006 18:02:00 +0100
Sent to CCL by: Eric Breynaert [eric.breynaert_._biw.kuleuven.be]
Thanks for the suggestions. I'm giving an overview below.
- SCF=qc will probably solve the problem, albeit at a cost
- Change the SCF converger to either SD, Quadratic or Fermi
- lower the symmetry of optimize with and optimize
with the "nosymm" keyword
I solved the problem using a variation on the
first suggestion. Normally the scf took less than
80 cycles to converge. So i
used scf=(Maxconventionalcycles=100,xqc) which
resulted in a good compromise between using
scf=qc and optimisation speed. In the case of the
DIIS error the scf always took more than 100
cycles before the error, so by adding
scf=(Maxconventionalcycles=100,xqc) the scf
switched to qc after 100 cycles in the standard DIIS mode.
Sent to CCL by: "Eric Breynaert" [Eric.breynaert]=[biw.kuleuven.be]
I'm trying to optimize a transition metal
structure using DFT ub3lyp LANL2DZ basisset for
the metal center , 6-31G(d) for all other elements o.a. O, H, C, S,
In most cases the optimisation succeeds. But
sometimes g03 generates the following error
after about 20 to 80 steps in the optimisation.
Density matrix is not changing but DIIS error= 2.02D-05 CofLast= 3.35D-01.
The SCF is confused.
I've already btried different approaches to get
arround this but nothing has succeeded. For
example, recalculating force constants on the
geometry obtained 1 or 2 steps before the error.
Forcing g03 to make a new guess at every step of
the optimisation using guess=(mix,always).
Has anyone encountered such a problem before, or
do you know a solution to it ?
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