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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