# [molpro-user] maxiter puzzle in multi

Haitao Ma mht at mrdlab.icas.ac.cn
Thu Apr 21 02:44:13 BST 2005

```Dear Molpro-user,

I got a puzzle as following, which had been posted here last year but
no reply. So I re-sent it here to get more suggestion.
*****from  CERMM, Concordia University*********
We are experiencing trouble getting our CASSCF calculations to
converge. We know that the selected active space is appropriate for
our system (O4), and we employ equilibrium geometry for different
isomers.
We usually get the calculation to converge more
easily by doing successive calculations with increasing active space
and required number of states.
In such calculation,

casscf;
occ,   20;
closed,8;
wf,32,1,0; state,1;
wf,32,1,2; state,7;
wf,32,1,4; state,1;

casscf;
occ,   20;
core,8;
wf,32,1,0; state,5;
wf,32,1,2; state,7;
wf,32,1,4; state,1;

casscf;
maxiter,100;
IPRINT,MICRO;            !print information on convergence problem
occ,   20;
closed,8;

the first casscf achieves convergence, but the next two won't, and
both print something like:

ITER. MIC  NCI  NEG     ENERGY(VAR)     ENERGY(PROJ)   ENERGY CHANGE
STEP       TIME

1   40   29    0    -299.46358617    -299.46327296    0.00031321
0.00605306 0.00000000 0.28965734
0.16D-01    907.83

*** NO CONVERGENCE ***

We faile to understand what parameters will determine the number of
interations, and what should be done to increse the number of
iterations. As you can see on below the second calculation, the maxiter
did
not seem to help.

CONVERGENCE PROGRESS
--------------------

CHANGE IN ENERGY
0                    0.001496911537             -299.463625399664
1                    0.000000000000             -299.436598472010
0.027026927654
(PROJECTED)

** WVFN ****  START OF ITERATION  2 AT TIME  1240.64

Entering internal optimisation at time  1254.91

Energy      DIIS

1  1  1298.62  0.00007543    0.00000000    1.00000000    0.00000000
-299.43659916     0
1  2  1298.66  0.00000020    0.00060323    1.00000000    0.00000000
-299.43659919     0
Too many P-space configurations for threshold      0.40
Actual threshold used:      0.34
2  1  1406.90  0.00086038    0.00060336    0.00391926    0.00084597
-299.40184999     0
2  2  1406.94  0.00000689    0.00873427    0.00391926    0.00000000
-299.40185670     0
3  1  1406.99  0.00000001    0.00874368    0.00000000    0.00000000
-299.40185670     0

CPU FOR TRAOPM:      1.33 ( 490.7 MFLOPS)  NOP_CORE=  40 NOP_FILE=   0
MINWK=   612061  NWUSED=  6372060
NWL= 89999500

End of internal optimisation at time    1408.33

ENERGY =   -299.4018566977  ENERGY CHANGE =   0.0617687020