[molpro-user] Non-convergence error in OPTG program

[Cayo Emilio]

Dear MOLPRO community.
I am trying to compute the energy of a 3-atom system using the program
MULTI in different multiplicities. The singlet works just fine, but triplet
is a headache
My input is:

 memory,200,m
 thresh,pspace=20
 basis=AVQZ
 SYMMETRY,X,Y

 R1=8.20 bohr
 R2=[0.5,1.0,1.5,2.0,2.25,2.5,2.75,3.0,3.25,3.5,3.75,4.0,4.5,4.75,5.0,5.5,6.0]
 theta1=90 deg
 theta2=0 deg
 theta3=-90 deg
 R3=1.0 bohr

 geometry={Si1;
   q1,Si1,R1/2;
   q2,q1,R3,Si1,theta1;
   Si2,q1,R1/2,q2,theta3,si1,theta2;
   Si3,q1,RR,Si1,theta1,q2,theta2}

 DO i=1,#R2
 RR=R2(i)
 R(i)=RR
 {multi;maxit,40;wf,42,1,2;state,2}
 {optg,maxiter=60,VARIABLE=energy(1)
  active,R1}
 RR1(i)=R1
 theta(i)=theta1
 ecas1(i)=energy(1)
 ecas2(i)=energy(2)
 table,R,ecas1,ecas2,RR1
 ENDDO

I am trying to approximate one of the atoms point-by-point to the dimer,
and usually after two or three points of the loop the MOLPRO crash with the
error: "No convergence. The problem occurs in Multi.". The log says
" WARNING: exit with wrong ci vector!!" for many interactions, what makes
no sense to me. Sometimes I try to reedit the input to start from the point
(of the R2 vector) it had just crashed and it goes fine, but after several
tries and small changes on my parameters values.
The problem occur only in triplet calculations, with all symmetries of C2v
group. The calculations for all four symmetries of the singlet state, for
the same parameters of the input above, end correctly.
If I do not give a higher thresh for p-space the program crashes with the
"Non-zero p-space gradient" error, precisely in the same point.

I appreciate any help.
Thank you,
Cayo E. M. Gonçalves.
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