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

[Evgeniy Gromov]

Hi Jeff,

Thanks for your response.

>> 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.

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 :(

Best regards,
Evgeniy

Jeff Hammond wrote:
> 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.
>
> Best,
>
> Jeff
>
> 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
>> Im Neuenheimer Feld 229
>> D-69120 Heidelberg
>> Germany
>>
>> Telefon: +49/(0)6221/545263
>> Fax: +49/(0)6221/545221
>> E-mail: evgeniy at pci.uni-heidelberg.de
>> _______________________________________
>>
>>
>>
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>> Molpro-user at molpro.net
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>
>
>


-- 
_______________________________________
Dr. Evgeniy Gromov
Theoretische Chemie
Physikalisch-Chemisches Institut
Im Neuenheimer Feld 229
D-69120 Heidelberg
Germany

Telefon: +49/(0)6221/545263
Fax: +49/(0)6221/545221
E-mail: evgeniy at pci.uni-heidelberg.de
_______________________________________