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

Gerald Knizia knizia at theochem.uni-stuttgart.de
Sat May 11 11:34:45 BST 2013

On Wed, 2013-05-08 at 11:41 +0200, Evgeniy Gromov wrote:
> Gamess-US can converge SCF "hands down" with an exponent 1.E-50 .
> Molpro however could do the same with 1.E-10. 1.E-15 or smaller
> didn't work :(

Unlike other programs, Molpro never throws away basis functions if they
become unreasonable. Are you sure that your 1e-50 exponent basis
function actually ended up the calculation? Because for such a function
even handling its normalization coefficient would be a serious problem.

While it is perfectly possible to calculate integrals over such
functions[1] (it is even done routinely with zero exponent functions for
implementing simpler integrals in terms of more complicated integrals),
using them as basis functions is very much not recommended. If you want
to try it anyway, be sure to turn off all integral screening,
compression, and approximation options.

[1] See JCTC 7 2387 (2011)
Gerald Knizia

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