## Firefly and PC GAMESS-related discussion club

Learn how to ask questions correctly

** Re: ISPIN filter for doublet states **
Alex Granovsky

gran@classic.chem.msu.su

Dear lello,the ISPIN filter only works if the number of alpha electrons is equal

to the number of beta electrons and so unfortunately it cannot be used

for doublets.

Try increasing nhgss, nstgss, and mxxpan in $det/$cidet groups.

NHGSS = dimension of the Hamiltonian submatrix which
is diagonalized to obtain the initial guess
eigenvectors. The determinants forming the
submatrix are chosen on the basis of a low
diagonal energy, or if needed to complete a
spin eigenfunction. The default is 300.
NSTGSS = Number of eigenvectors from the initial guess
Hamiltonian to be included in the Davidson's
iterative scheme. It is seldom necessary to
include extra states to obtain convergence to
the desired states. The default is the value
for NSTATE.
MXXPAN = Maximum number of expansion basis vectors in the
iterative subspace during the Davidson iterations
before the expansion basis is truncated. The
default is the larger of 10 or NSTGSS+1. If this
value is decreased, convergence is hurt but the
memory required is decreased.

Hope this helps.

Kind regards,

Alex Granovsky

On Wed May 15 '13 5:05pm, lello wrote

-------------------------------------

>Hi all,

>I have read on the forum that it is possible to improve the convergence of SA-MCSCF using ISPIN keyword to generate a better selection of initial states (for ALDET method).

>ISPIN=0 filters all odd spin numbers and ISPIN=1

>filters all even spin numbers.

>What about doublet states? Is is possible to improve the initial

>guess for doublets?

>lello

Wed May 15 '13 9:47pm

This message read **859** times