Subject: Quasi-Realtivistic ECP

From: Jeffrey Webb <[email-masked]>
Date: Tue, 21 Mar 2000 11:40:47 -0500 (EST)

Dear CCl'ers,

What are quasi-realtivistic potentials and how do they differ from normal
ECP's???

Are they any quasi realtivistic ECP's for iodine which can be used in DFT
calculations??

Thank you in advance.

[email-masked]
Jeff Webb

---

From: "Stefan Fau" <[email-masked]>
Date: Tue, 21 Mar 2000 13:51:42 -0500

Hi Jeffrey,

quasi-relativistic ECPs include some of the relativistic effects (the
scalar ones) and
ignore other effects like e.g. spin-orbit coupling. Experience shows
that quasi-
relativistic ECPs are necessary for elements of the 5th and higher
periods. Apart
>from reducing calculational time, they improve the results notably.

An alternative is the inclusion of scalar relativistic operators into
the Hamiltonian
(or to apply them perturbatively to the reference wavefunction; I
don't remember
too exactly) like it is possible in e.g. ADF.

In the case of transition metals it is a good idea to use small core
ECPs which treat
the electrons of the sub-valence shell explicitly.

A good choice for ECPs (quasi-relativistic and other) are the
Stuttgart-ECPs by
Stoll, Preuss et al.. They are available at:
http://www.theochem.uni-stuttgart.de/
Another good source for ECPs and basis sets is
http://www.emsl.pnl.gov:2080/forms/basisform.html
or it's european mirror site:
http://wserv1.dl.ac.uk:800/emsl_pnl/basisform.html

Stefan
______________________________________________________________________
Dr. Stefan Fau
[email-masked]
Quantum Theory Project
(352) 392-6714
University of Florida
Gainesville, FL 32611-8435

---

From: Huajun Fan <[email-masked]>
Date: Tue, 21 Mar 2000 13:40:55 -0600

> >from reducing calculational time, they improve the results notably.

Dear Stafan,  How would I know if the basis set I used includes quasi-relativistic
ECPs?  Say I am using LANL2DZ basis set for Ir atom, is that the one?  Is there a
good reference I can read about it?  Many thanks.

huajun

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