[molpro-user] Too low energies in CI

[Kirk Peterson]

Lukas,

I guess you mean that your atomic excitation energies are too low compared to experiment?  It would help
to know which atoms you are working on.  There are several factors, of course, that lead to non-complete
agreement with experiment and the basis is an important factor but not the only one. Insufficient electron
correlation, both valence and core, are always partly to blame, as is the method used to recover spin-orbit effects.  Unless
we have more details it's difficult to propose anything.

regards,

Kirk


On May 6, 2011, at 4:41 AM, Łukasz Miądowicz wrote:

> Hello,
> 
> I have a quastion when I'm doing my calculations in Molpro for
> diatomic molecule I have always too low energies in the atomic limit
> comparing to spectroscopic data from Moore's tables.
> 
> How can I increase those energies ?
> 
> I tried to expand the basis set with both polarization and diffuse
> function but from some point of my expansion the result stops at the
> same level so in the atomic level I have the difference between the
> experimental data 20 cm^-1 and further expansion of the basis set
> doesn't change the result..
> 
> 
> what should I do ? should I do maybe something with CPP ? How can I
> improve my calculations?
> 
> Thank you in advance,
> 
> Lukas
> 
> -- 
> Department of Theoretical Physics and Quantum Information
> Faculty of Applied Physics and Mathematics
> Gdansk University of Technology
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