[molpro-user] cannot get rohf to converge with larger basis sets

Benj FitzPatrick benjfitz at uchicago.edu
Wed May 27 18:54:50 BST 2009

I'm using molpro 2008.1, patchlevel 31 and I'm having some problems with hf
converging using larger basis sets (aug-cc-pvdz and larger).  

 * The molecule is an open-shell doublet (input file and {locali,pipek;}
localized orbitals in molden format are attached), and this problem occurs for
both the cis and the trans conformers.

* 6-31G*, 6-311G**, and cc-pvdz converge, but adding diffuse functions or higher
angular momentum functions leads to non convergence.

 * I used mcscf to look at the first excited state and it is much higher in
energy (X = -191.420511770210, A = -191.295282002574) so there shouldn't be any
problems arising from a low-lying excited state.  Below is the ci vector output
as well showing X is pretty much dominated by one configuration.

 CI vector

 22222a000      0.9504701   0.0484423
 2222a2000     -0.0424724   0.7432273
 222220a00      0.0301000  -0.5814224
 2222a0200     -0.0020958  -0.2024822
 222202a00     -0.0073925   0.1907678
 2222aba00      0.1780930   0.0206321
 22220a200     -0.1285216  -0.0151333
 2222baa00     -0.1020188  -0.0095914
 22202a020     -0.0885933  -0.0053440
 2222aab00     -0.0760742  -0.0110408
 2220a2020      0.0030896  -0.0686470
 22022a002     -0.0611572  -0.0061246
 222020a20     -0.0029005   0.0538511

 * UHF has no problems converging (I even tried with aug-cc-pvtz).

 * I tried adjusting the level shifts, but I wasn't able to find a combination
that worked.  This was guess work on my part, so any tips for adjusting these
sanely would be great.

 * I repeated these calculations for the transition states leading away from
this reactant and none of them had any problems.

 * C1 symmetry (nosym) was used for all of the calculations.

Any help would be greatly appreciated.
Benj FitzPatrick
University of Chicago
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