[molpro-user] An interesting and confused problem

[Wang Bingwu]

Dear Molpro users,

I have encountered an confused problem several times. The converge status of
CASSCF calculation is related with the execution time. For example. I do a
CASSCF computation with the following input:
"
 ***,title the test of molpro
 gprint,orbital,basis,civector
 memory,250,m
 geometry={
 Sc
 Cr 1 Rmn
 }
 basis
 spdf,Sc,Bauschlicher-ANO
 C;
 spdf,Cr,Bauschlicher-ANO
 C;
 end
Rmn=2.0 ang
 uhf;
 occ,15,5,5,1
 closed,11,4,4,0
 wf,45,1,7
 multi;
 occ,16,6,6,2
 closed,10,4,4,0
 core,10,4,4,0
 wf,45,1,7
 orbprint,5
 maxiter,30
---
"

When the job was run at Jan 27, 2006, it is successful, the CASSCF section
converged. But after that, the job failed with error message:
"
 ITER. MIC  NCI  NEG     ENERGY(VAR)     ENERGY(PROJ)   ENERGY CHANGE
GRAD(0)  GRAD(ORB)   GRAD(CI)     STEP       TIME


 NON-ZERO P-SPACE GRADIENT. LARGEST VALUE:    0.17D+02
 Probably the p-space is not closed under symmetry operations. This can
happen if
 the initial orbitals are not symmetry adapted or if there is root-flipping
between states of
 different symmetry. Try different p-space threshold, or select p-space
configurations manually.
 The check can be bypassed by setting thresh,pspace=thr to a larger value.
 Non-zero p-space gradient elements smaller than thr are ignored.
"
 I ran it several times after Jan 27, 2006, but it all failed with the same
error message. Now I change the system clock to the "right time" Jan 27,
2006, it runs OK.  Is it interesting? but it is a disaster for an ab initio
calculation.

There are several other examples like this before, it is not a unique
incident. Is this a bug of Molpro ?  How to overcome it? Thank you.

Best regards,
Wang Bingwu

Chemistry Department, Peking University
Beijing, China
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