Subject: high-quality GAMESS-US basis set for iodine?

From: ASG <[email-masked]>
Date: Wed, 29 Dec 1999 20:32:09 -0500

Having reviewed past CCL messages on the subject, I'm aware of the fact
that the question has been asked before--but no good answer to be
found...  Is it possible that there are none available?  The oft-cited
PNL site offers a bunch of basis sets for iodine:

STO-3G
3-21G
MIDI!
WTBS
Sadlej pVTZ
LANL2DZ ECP
SBKJC VDZ ECP
CRENBL ECP
Stuttgart RLC ECP
DZVP (DFT Orbital)
DeMon Coulomb Fitting
DGauss A1 DFT Coulomb Fitting
DGauss A1 DFT Exchange Fitting
Ahlrichs Coulomb Fitting
Huzinaga Polarization

but, at least to my untrained eye, none of them seem to be of high
quality, esp. if an all-electron basis set ready-made for use in
GAMESS-US is sought.  The Sadlej pTZV set is not well optimized, at
least based on my reading of the attached comments. I don't want to (or
can't) use ECP and DFT bases, don't know anything about the last two.

Why the problem?  Somebody was asking why [ICl2]- is linear, and I tried
to use the GAMESS-US/MolDen duo to take a look at the orbitals, bonds
etc., and noticed that the bond length at the 3-21G(d) level is wrong by
0.07 A.  And then started looking for a better basis set, and...couldn't
find it.  I realize the general picture at the HF/3-21G(d) level should
be correct, but I'd love to have something closer to 6-311+G(d)
basis--or better.

What do the professionals use to get good geometries and energies of
iodine compounds, even as simple as HI?  How much better can MIDI! be
than 3-21G* in this situation? Is my aversion to ECP justified?  I
appreciate any comments.

I should note that doing such calculations are just a hobby to me to
better understand the compounds I'm working with in an otherwise very
practical millieu...

Happy Y2K to everybody!

Tony Gozdz
[email-masked]