[molpro-user] CI convergence

[S. Horvath]

Hello all,

I am extremely new to Molpro, and as such I am trying to run a 
MR-SO-CISD calculation for the six lowest electronic states of the 
molecule IBr- using ECPs. I am having convergence issues with the 
Multi-reference internally contracted CI program (prior to any 
spin-orbit stuff), even though the error message sounds like it pertains 
to the MCSCF program not being converged. Moreover, I can truncate the 
calculation to only run the MCSCF, and the calculation finishes, which 
leads me to believe that the problem lies with the MRCI program.

Error:
 ?Error: MCSCF not converged. This error exit can be avoided using the 
IGNORE_ERROR option on the ORBITAL directive

The error message then the "ignore-error option," but I don't really 
know how this would affect the results of my calculation if I ignore the 
fact that the MRCI/MCSCF is not converged.

I've looked through the manual and have not found anything helpful. I've 
tried the "maxiter" keyword, but to no avail. I also read that the 
convergence issues arise because the active space is not chosen 
properly; however, I can run the same calculation at the equilibrium 
distance (~ 3.12ang) instead of at 12ang (which is what I want...), and 
the calculation runs to completion. It sounds like the larger 
internuclear distance is adding an extra lay of difficulty to the 
calculation, but I'm not sure how or why.

On a related note, does anyone know why for the calculation at the 
equilibrium, the SO energies of my 6 states are listed twice? Is this a 
major problem, or just a silly bug when writing the energies to the 
output file? Just curious.

Below is my input file for 12.0 ang. Any advice that you can provide 
would be most appreciated.

Thanks so much,
Samantha Horvath

=============================
***,ibr-
memory,500,M !4 GB memory
gprint,basis,orbital,civector
gthresh,orbital=1.d-6,civec=1.d-6
molecule='IBr-'

geometry={I;
          Br,I,R}
R=12.00 Ang

basis={
ecp,i,ECP46MDF;
sp,i,ECP46MDF;c;
s,i,0.030;
p,i,0.023;
d,i,0.3550,0.1851,0.1025;
f,i,0.4330,0.2026;

ecp,br,ECP28MDF;
sp,br,ECP28MDF;c;
s,br,0.041;
p,br,0.030;
d,br,0.7062,0.2639,0.1047;
f,br,0.5515,0.2580;
}

cpp,init,2;
I,2,1.028,,,1.247;
Br,2,0.266,,,2.259;

{hf;wf,15,1,1;orbital,2100.2}      !SCF to obtain sample wf. Used 
ground-state config.

{mcscf;maxiter,50;failsafe;
occ,5,4,4,0;
closed,2,0,0,0;
wf,15,1,1; state,2; weight,0.1,0.1;
wf,15,2,1; state,2; weight,0.1,0.5;
wf,15,3,1; state,2; weight,0.1,0.1;}

{ci;maxiter,50;occ,5,4,4,0; closed,2,0,0,0; wf,15,1,1; state,2; 
weight,0.1,0.1; noexc; save,3010.1}
{ci;maxiter,50;occ,5,4,4,0; closed,2,0,0,0; wf,15,2,1; state,2; 
weight,0.1,0.5; noexc; save,3030.1}
{ci;maxiter,50;occ,5,4,4,0; closed,2,0,0,0; wf,15,3,1; state,2; 
weight,0.1,0.1; noexc; save,3050.1}

{ci;maxiter,50;occ,5,4,4,0; closed,2,0,0,0; wf,15,1,1; state,2; 
weight,0.1,0.1; save,4010.1}
{ci;maxiter,50;occ,5,4,4,0; closed,2,0,0,0; wf,15,2,1; state,2; 
weight,0.1,0.5; save,4030.1}
{ci;maxiter,50;occ,5,4,4,0; closed,2,0,0,0; wf,15,3,1; state,2; 
weight,0.1,0.1; save,4050.1}

lsint      !call spin-orbit code

!so calc w/ mcscf
{ci;maxiter,50;hlsmat,ecp,3010.1,3030.1,3050.1} !rerun CASSCF with SO info

!SO calc w/ mrci
{ci;maxiter,50;hlsmat,ecp,4010.1,4030.1,4050.1} !rerun CI with SO info

-- 
Samantha Horvath
McCoy Research Group
2144 Newman-Wolfrom
*********************
120 W. 18th Ave.
Box #234
Columbus, OH 43210
614-688-8180