Subject: summary: cluster calculations

From: Hua-Jun Fan <[email-masked]>
Date: Mon, 19 Apr 1999 13:34:37 -0700 (MST)

Dear CCL'ers,

 The original question and the replies received up to now are shown
 below(selected contents only).  Many thanks to to David Case, Thomas
Gray, and T.R. Hughbanks.  

Huajun

----origianl question-------
I had question about using DSW-Xalpha methods in calculating Re6 cluster.
I have read a paper about it and am interested in repeating the
calculations.  The authors's email address on the paper is not right.  The
paper is published by Dr. Arratia-perez on J. Chem.Phy. vol 110, num.  5,
1999 Feb issue about DSW-Xalpha calculation on Re cluster.

I wonder if anyone have any suggestion/advice on the software
availability, and a bit of detail about it how the calculations are
performed, even the priciple about the methods, calculations. (I am quite
new to this area, all I knew about it is not very many methods are
available to do this kind of cluster) From paper, there is not much
information in it.

---- replies -----
#############T.R. Hughbanks#########
[email-masked]

  We have performed a number of calculations on clusters in recent years.
These days, we use primarily density functional theory.  We have used the
DMol and DSolid modules within the MSI suite of programs (formerly the
Biosym package).  This method is computationally efficient, but the
numerical grids used in evaluating the exchange and correlation
functionals seem to me to be a bit suspect when numerical precision is
concerned (i.e., as in a careful geometry optimization).  The BLYP
functional is built in to the version we have used, but not the B3LYP
functional (the latest and most "popular" version).
  DFT methods are built into the latest Guassian packages, though they run
slower than Hartree-Fock in Guassian's implementation (in which 3- and
4-center integrals are still evaluated, in DMol the electron density is
expanded in auxilary functions so such integrals are avoided).  If you
want to do calculations in rhenium clusters, you will have to face the
problem of what to do about relativistic effects.  Ignoring such effects
in 2nd row T.M.s is not too serious, but most experts will tell you that
you can't really neglect them for 3rd row T.M.s.  A fairly recent paper
that compared Nb6X12 and Ta6X12 clusters appeared (in JACS or Inorg.
Chem.).  That is probably a good reference to look up in order to get you
started thinking about DFT calculations On Re6-based clusters.

#############David Case:#############
[email-masked]

You can try to reach Dr. Arratia-Perez at the following e-mail address:

    [email-masked]

However, this address is about 10 months old, and may still not work.
(It looks like there is just a typo in the e-mail address in the JCP
paper.)

The code for the DSW-Xalpha program is available from our anonymous
ftp site:

     ftp://ftp.scripps.edu/pub/case/dsw.tar.Z

There should be a README file (I think in the dsw directory).  This points
you to the instructions (in main.f or somewhere like that).  You will
probably need to study how the non-relativistic program works first, as it
has much fuller documentation.  I hope you will be able to get in touch
with Dr. Arratia-Perez, since he would be an excellent source of help.

To understand the method, you should trace back to previous papers of
Arratia-Perez.  The basic algorithmic reference is the following:

C. Y. Yang and D. A. Case.  Dirac scattered wave
calculations.  Local Density Approximations in Quantum Chemistry
and Solid State Physics, J. P. Dahl and J. Avery, eds.
(Plenum, 1984), pp. 643-664.

This might be a little hard to find now(!).  The first calculations using
the method were the following, which has a fair description of the
approach:

D. A. Case and C. Y. Yang.  Relativistic scattered wave
calculatons on UF6.  J. Chem. Phys.  72, 3443-3448 (1980).

############Thomas Gray########
[email-masked]

Bursten, B. E.; et al. Isr. J. Chem. 1980, 19, 132.

Woolley, R. G. Inorg. Chem. 1985, 24, 3519-3525.

Hughbanks, T.; Hoffmann, R. J. Am. Chem. Soc. 1983, 105, 1150-1162.

Hughbanks, T.  Inorg. Chem. 1986, 25, 1492-1497.

Saito, Y.;  Tanaka, H. K.; Azumi, T. J. Phys. Chem. 1985, 89, 4413-4415.

Azumi, T.; Saito, Y. . Phys. Chem. 1988, 92, 1715-1721.

Imoto, H.; Saito, T.; Adachi H. Inorg. Chem. 1995, 34, 2415-2422.

Robinson, L. M.; Bain, R. L.; Shriver, D. F.; Ellis, D. E. Inorg. Chem.
1995, 34, 5588-5596.

Two recent reviews which discuss electronic structure calculations are:
Saito, T. Adv. Inorg. Chem. 1996, 44, 45-92, and Prokopuk, N.; Shriver, D.
F. Adv. Inorg. Chem. 1998, 46, 1-50.