Subject: Re: Help for DeFT work?

From: Hu Hao <[email-masked]>
Date: Mon, 6 Oct 1997 21:13:02 -0700 (PDT)

Dear CCLers,

Weeks ago I've posted a mail about the DeFT optimization of water
dimer. Thanks for replies from Dr. Frederic A. Van-Catledge and
Dr. Rudolf Herrmann.

I have solved the problem now. There are two main reasons responsible
to the results.

The first is the basis sets used. The problem could be partly solved 
by using larger basis sets, e.g., using DZVP4 or TZVP basis as AO 
basis, and A3 or A4 basis as auxiliary basis.  

The second is as what Dr. Rudolf Herrmann said : "The functionals 
currently available for DF calculations are not meant to treat
long range interactions such as Van der Waals forces, which should
be highly important for your water dimer. DFT will be well suited
for, lets say, an ice crystal, but not for this case of a water 
dimer." It seems that the system of water dimer needs careful
consideration when studied.

Sincerely

Hao Hu
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     Hao Hu
     2-615, West Campus, USTC    Email: [email-masked]
     Hefei, Anhui 230026         WWW  : (suspended)
     P.R.China                   Tel  : 0551-3603754
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