Subject: Scalar vs. SO relativistic effects

From: [email-masked] (Georg Schreckenbach)
Date: Wed, 5 Jan 2000 11:02:11 -0600

Dear all,

I got the following message as a response to my earlier post (included below).
I thought that it might be of some general interest, so I am posting it, with
permission, to the general list.

Best regards, Georg

>Dear Georg,
>
>I ws interested in your response below, and wanted to bring to your
>attention a couple of papers that Clint Nash and I published this year on a
>wonderful ficititious molecule [118]F4 (the paper was published _before_
>[118] was discovered!).  With scalar relativistic effects we predict the
>molecule to be square planar like XeF4.  But when SO effects are included,
>the molecule very slightly prefers a tetrahedral geometry.
>
>The relevant papers:
>
>C. S. Nash and B. E. Bursten, “Spin-Orbit Coupling vs. the VSEPR Method:
>On the Possibility of a Nonplanar Structure for the Super-Heavy Noble-Gas
>Tetrafluoride [118]F4,” Angew. Chem., 111, 115-117 (1999); Angew. Chem.
>Int. Ed. Engl., 38, 151-153 (1999).
>
>C. S. Nash and B. E. Bursten, “Spin-Orbit Effects, VSEPR Theory, and the
>Electronic Structures of Heavy and Superheavy Group IVA Hydrides and Group
>VIIIA Tetrafluorides.  A Partial Role Reversal for Elements 114 and 118,”
>J. Phys. Chem. A, 103, 402-410 (1999).
>
>I hope you find them of interest.
>
>Best regards, Bruce
>
>>Date: Mon, 3 Jan 2000 11:34:30 -0600
>>To: [email-masked] (CCL)
>>From: [email-masked] (Georg Schreckenbach)
>>Subject: CCL:so effects on geometry (was: high-quality GAMESS-US basis set
>for
>>iodine?)
>>
>>Dear Valentin and CCL,
>>
>>>Does anybody know appropriate references on what effect: scalar-
>>>relativistic or spin-orbit has more effect on geometry?
>>
>>There is one paper out by van Lenthe et al. where they compared scalar and
>>spin-orbit effects on the geometry and other properties of small molecules.
>>For instance, for I2, they find a difference in bond length of 0.019
>Angstrom,
>>one of the largest for the set of molecules considered. So, the conclusion
>>was that the influence of spin-orbit effects on the geometry of closed-
>>shell molecules is modest only. The same is not true, of course, for other
>>properties including energetics or NMR. The reference is JCP 1996, 105, 6505.
>>
>>   Besides, it is clear that one needs scalar relativistic effects to get the
>>geometries right, cf., e.g., the classic 1988 Chem Rev. review by Pyykkö.
>This,
>>then, is a point in favor of ECP basis sets for something as heavy as iodine
>>:-)
>>
>>>In most cases using ECP usually gives better agreement in geometry
>>>compared to all-electron calculations for iodine containing molecules.
>>>For example, one may take a look at recent publications with Stuttgart
>>>ECP basis set on iodine.
>>
>>Best regards, Georg
>>

>* * * * * * * * * * * * * * * * * *
>Bruce E. Bursten
>Distinguished University Professor and Department Chair
>Department of Chemistry
>The Ohio State University
>100 W. 18th Avenue
>Columbus, OH 43210
>
>Chair's office:         (614) 292-6723
>                                        (614) 292-3311
>Research office:        (614) 292-1866 (voice)
>                                        (614) 688-3306 (fax)
>E-mail:                 [email-masked]
>

--
==============================================================
Dr. Georg Schreckenbach           Tel:     (USA)-505-667 7605
Theoretical Chemistry T-12        FAX:     (USA)-505-665 3909
M.S. B268, Los Alamos National      E-mail:  [email-masked]
Laboratory, Los Alamos, New Mexico, 87545, USA
Internet:    http://www.t12.lanl.gov/home/schrecke/
==============================================================