[molpro-user] The smallest exponent that can be used to specify a basis function

Jeff Hammond jhammond at alcf.anl.gov
Tue May 7 19:10:08 BST 2013

While I have no specific expertise in the Molpro code, I cannot
foresee a circumstance where this is anywhere close to numerically
stable in any quantum chemistry code that computes with double
precision numbers.  It would not surprise me if most integral codes
were unstable for exponents less than 1e-3 (again, double precision is
assumed), but this is just speculation.

If you want an orbital for an unbound electron, you should use an
appropriate basis function rather than trying to hack a plane wave
from a gaussian.



On Tue, May 7, 2013 at 11:30 AM, Evgeniy Gromov
<Evgeniy.Gromov at pci.uni-heidelberg.de> wrote:
> Dear Developers and Users of Molpro,
> I wonder what is the smallest exponent that can be used
> to specify a basis function. I am interested in putting
> just *one* basis function with the exponent let's say 1.E-15.
> But SCF does not converge in this case. I have a feeling that
> this might be a technical problem.
> Best regards,
> Evgeniy
> --
> _______________________________________
> Dr. Evgeniy Gromov
> Theoretische Chemie
> Physikalisch-Chemisches Institut
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> E-mail: evgeniy at pci.uni-heidelberg.de
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Jeff Hammond
Argonne Leadership Computing Facility
University of Chicago Computation Institute
jhammond at alcf.anl.gov / (630) 252-5381
ALCF docs: http://www.alcf.anl.gov/user-guides

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