X-ALPHA, DFT TODAY:SUMMARY
Thurs 2000 July 6
Here is a summary of the answers to my X-alpha question. I thank all who
responded (#1--#4).
Question:
> > Monday 2000 June 12
> >
> > Hello,
> >
> > the Xalpha method, developed by John slater (1951) mainly for solids
and
> > atoms, and used till at least the early 1970's , was perhaps the
first
> > really useful DFT method. For molecules it has now been replaced by
> > Kohn-Sham-based approaches to DFT.
> >
> > (1) Is the Xalpha method still used for solids/crystals (e.g. by
> > solid-state physicists?). If not, what replaced it?
> > (2) In modern molecular DFT, probably the most popular method is
> > B3LYP/6-31G*. What seems to be the second most widely-used?
> >
> > Thanks
> > E. Lewars
====
Answers
#1
Dr Robert J. Doerksen, rjd |-at-| bastille.cchem.berkely.edu
> Dear Dr. Lewars,
>
> I just have a small comment on (1):
> You may be amused by the article Dennis Salahub wrote giving a
> retrospective on the X-Alpha method, in Theoretical Chemistry
Accounts,
> in their 20th century highlights issue:
>
> Dennis R. Salahub: From X<alpha>-scattered wave to end-of-the-century
> applications of density functional theory in chemistry. Perspective
on
> "Chemical bonding of a molecular transition-metal ion in a crystalline
> environment" (Johnson KH, Smith FC Jr (1972) Phys Rev B 5: 831-843)
>
> That's in: Theor Chem Acc 103 (2000) 3/4, 311-312
>
> Cheers,
>
> Robert
>
> Dr. Robert J. Doerksen
*************************************************
> Head-Gordon Group
*
> Department of Chemistry work phone (510)
642-9304
> University of California fax (510)
643-6232
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> **** webpage:
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---
#2
Per-Ola Norrby, peo |-at-| dfh.dk
Hi,
>
> >(2) In modern molecular DFT, probably the most popular method is
> >B3LYP/6-31G*. What seems to be the second most widely-used?
>
> I'd vote for BP86. It's been around longer, is almost as
> accurate, and substantially faster (at least in some codes...).
>
> /Per-Ola
> --
>
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> * Per-Ola Norrby, Associate Professor
> * The Royal Danish School of Pharmacy, Dept. of Med. Chem.
> * Universitetsparken 2, DK 2100 Copenhagen, Denmark
> * Tel. +45-35306506, fax +45-35306040
> * Email: peo |-at-| dfh.dk (preferred), peo |-at-| compchem.dfh.dk
> * WWW: http://compchem.dfh.dk/PeO/
------------
#3
Thomas Heine, Thomas.Heine |-at-| chiphy.unige.ch
> (1) mainly LDA, later on GGA was used as well
> (2) B3LYP is the mostly used by chemists, it is almost never used by
> physicists, since (i) they don't like HF exchange since it makes the
> programs very slow, (ii) it just works well for lighter elements.
> Perdew-Wang 96, PW91 and the newer PBE is used quite often, I think in
a
> competitive amount with old-fashioned LDA (e.g. VWN).
>
> Thomas
> University of Geneva
>
> PS: Let me know what others tell you
---------
#4
Thomas Bligaard Petersen, bligaard |-at-| fysik.dtu.dk
Hello,
>
> I propose a response to question 1:
>
> The Xalpha was also replaced by the Kohn-Sham approch. In solid state
physics the
> LDA (of Kohn-Sham) was the most used exchange-correlation functional.
The role was
> taken over by the LSDA (Gunnarson and Lundquist) that describes
magnetic systems
> better. These are still used, and especially in more theoretical part
of solid
> state theory, as they are some of the only true ab-initio approches in
DFT. For
> applications the PW91 (Perdew-Wang) has become very important, as it
corrects some
> important deficiencies of the LDA. The PBE (Perdew-Burke-Ernzerhofer)
removes
> some problems of oscillating xc-potential in the PW91, whereby the
numerical
> behaviour of the calculations are somewhat improved. Other then that
it yields
> results very similar to PW91, and has more or less replaced the use of
PW91 today.
> The B3LYP yields quite bad results in solids, this is probably related
to the
> Hartree-Fock approch having some problems here. In the future orbital
dependent
> potentials are probably going to have growing importance in solid
state physics,
> but the selfconsistent implementation of these functionals are not yet
in common
> use, even if the functionals appear to give vastly improved results
for some
> systems. One such functional is the PKZB meta-GGA
(Perdew-Kurth-Zupan-Blaha).
>
> In short the LSDA and the PBE are the most used today.
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