| 12:48:11 PM PDT - Sun, Sep 28th 2014 |
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Hello,
I am using NWChem 6.5 to run MP2 gradient calculations on a water molecule including basis functions from a neighboring "dummy" water. This is part of a fragment calculation of bulk water and is carried out in the field of many (~500) Bq charges located on all atoms. The Bq charges are zeroed out on the water molecule undergoing QM calculation, but they remain on the dummy atoms.
The SCF seems to converge reliably, the MP2 and SCS-MP2 energies are displayed without error, and the ensuing CPHF converges as well. The problem arises after the SCF+MP2 dipole moments are displayed, when I get the error message "MAXITS exceeded in inv_it ... Eigenvector 102 failed to converge in inv_it3". I have found that this error does not show up if I a) reduce the basis set from cc-pVTZ to aug-cc-pVDZ, b) remove the embedding Bq charges, or c) remove the dummy basis functions.
I was unable to find anything related to this error by searching, except that the error originates from peigs/src/c/inv_it3.c . I tried increasing MAXITS to 50 and relinking; this did not solve the problem. I would greatly appreciate any advice in resolving this issue. If it is useful, here is an excerpt of the input file causing the problem:
charge 0
geometry units angstroms noautosym noautoz nocenter
O -3.3616227100 -6.4021920739 -4.0252337111
H -3.3418274500 -7.3347605539 -3.6903975311
H -2.5429073800 -5.9567577939 -3.6902536011
bqO -7.8872037600 -6.4986997339 -4.0865289411
bqH -8.6841039100 -6.0182355039 -3.7443051411
bqH -7.0947182700 -5.9945892039 -3.7723052511
end
basis spherical
* library cc-pVTZ
bqO library O cc-pVTZ
bqH library H cc-pVTZ
end
scf
thresh 1e-8
print low
end
mp2
freeze atomic
tight
end
bq units ang
-3.3616227100 -6.4021920739 -4.0252337111 0.00000000
-3.3418274500 -7.3347605539 -3.6903975311 0.00000000
-2.5429073800 -5.9567577939 -3.6902536011 0.00000000
-3.4056916800 -1.3275516739 -0.4798034611 -1.04623000
-2.6143601900 -1.7951296639 -0.1120830411 0.52620000
-3.3531110200 -0.3890048939 -0.1673309911 0.52003100
(....another ~500 charges here...)
end
task mp2 gradient
Thanks for looking!
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