Subject: Summary: van der Waals parameters from ab initio calc

From: [email-masked]
Date: Thu, 2 Feb 95 14:07:19 +0100

10 days ago I submitted the following question to CCL, the answers I got are
appeded: 

Subject: van der Waals parameters from ab initio calc?

Hi netters!

Could you please tell me how to derive van der Waals parameters from ab initio
calculations!
Any suggestions are wellcome (references, principles,...).
I'm interested in practical as well as theoretical approaches to this problem.
If I got interesting response, I'll collect them and post it to this group!

Thank you for help!

Thomas

Thomas Huber
Institut fuer Physikalische Biochemie 
der Universitaet Muenchen
Schillerstrasse 44
80336 Muenchen
Germany
email: [email-masked]

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Dear Huber:

     Thank you for posting such interesting question.  Eventhough I can not
give you answer, but I would like to see the summary if you can get enough.
Thank you very much in advarce

                                                    With my best regards

                                                    yuli  qin

                                         [email-masked]
 
From: [email-masked] (Joerg Hill)
Hi,
sorry for wasting bandwidth, but a direct response did not work.

Van-der-Waals parameters for repulsion can be obtained from ab initio
calculations using a test particle ansatz. The most papers have been
published by Ahlrichs:

H.-J. Boehm, R. Ahlrichs: JCP 77 (1982) 2028
H.-J. Boehm, R. Ahlrichs, P. Scharf, H. Schiffer: JCP 81 (1984) 1389

are the both basic paper. Applications can be found in:

H.-J. Boehm, C. Meissner, R. Ahlrichs: Mol. Phys. 53 (1984) 651
K. P. Sagarik, R. Ahlrichs, S. Brode: Mol. Phys. 57 (1986) 1247
K. P. Sagarik, R. Ahlrichs: Chem. Phys. Letters 131 (1986) 74
K. P. Sagarik, R. Ahlrichs: JCP 86 (1987) 5117
J.-R. Hill, J. Sauer: JPC 98 (1994) 1238

A new paper, which considers anisotropy is:

A. J. Stone, C.-S. Tong: JCC 15 (1994) 1377

I don't know any papers concerning the derivation of dispersive parameters
>from ab initio calculations. But dispersion requires electron correlation
and since these calculations are rather expensive, it could be that noone
has triesd it so far. Density Functional calculations could change this.

Tschuess
Joerg

P.S.: host name Physik.TU-Muenchen.DE NOT FOUND.

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Servus,
We are interested in the ineraction of helium with small to 
medium small (10 - 200 atoms) molecules. We found that with the MM3 vdW
parameters (Theochem, 312 (1994) 69), we can reproduce our experimental
results (gas phase mobilities) very well. I also tried to calculate
vdW parameters for He-He and H3C-H - He. In order to get the attractive
part of the potential right, one has to throw in a lot of correlation (CCSD(t))
and large basis sets (tripple zeta+pol.+diffuse). The repulsive part
of the potential on the other hand is well described by plain SCF + small basis
set. I did a scan of the pot. surface of H3C-H - He and found that fitting
a 12-6 potential to the scan gives very poor agreement while an exp.-6
potential is much better. The well depth and the position for these two
systems seems to be in reasonable good agreement with the MM3 parameters.

Contact me if you want to know more about what we are doing,

....Gert

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+ Gert von Helden, Dept. of Chemistry, UCSB, Santa Barbara, CA 93106 +
+ Tel   : 805-893-2673, Fax   : 805-893-8703                         +
+ E-mail: [email-masked]                                     +
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

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|> Thomas Huber wrote:
|> Could you please tell me how to derive van der Waals parameters from 
|> ab initio calculations!
|> Any suggestions are wellcome (references, principles,...).

For condensed matter, there is a fundamental problem with the
derivation of non-bonded interactions from ab initio calculations on
isolated molecules.  High quality ab initio calculations include
wavefunctions with quite large spatial extents, much larger than
existence in a condensed matter environment would allow.  So, if you
are going to calculate non-bonded interactions, you need to start with
realistic calculations including multiple molecules.  The energy of
interaction is straightforward.  Deciding how much of it is "van der
Waals" is another issue.

David States

From: [email-masked] (Ross Underhill)
Subject: Re: CCL:van der Waals parameters from ab initio calc?

>Could you please tell me how to derive van der Waals parameters from ab initio
>calculations!
>Any suggestions are wellcome (references, principles,...).
>I'm interested in practical as well as theoretical approaches to this problem.
>If I got interesting response, I'll collect them and post it to this group!

A very interesting question and one I have tried to deal with myself.  For
some elements you can put together two diatomics and bring them together
using ab initio calcs and plot the total energy.  You can then fit the
calculated energy as a function of separation.  I have done this in a few
cases.  I've even done it for methane.  You really should do it using UHF
since a lot of the attraction at long distances has to do with correlation
energy.  Obviously this scheme will not work for some elements that don't
make diatomics or small simple molecules.  There is also the point that this
only seems to make sense for closed shell systems.  It seems to me I saw
some references on deriving VDW parameters on the AMBER WWW site.  You might
want to look there.  I picked up some F parameters there.

Dr. Ross Underhill
Royal Military College of Canada
Kingston, Ontario
(613) 541-6000 X6175

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A possible reference for Nonbonding interactions from ab initio calculations
may be:

Dinur, U. and A.T. Hagler, J. Am. Chem. Soc., 111, 5149-5151, 1989.

Hope this helps.

Tahmid Mizan 
University of Michigan

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Thomas

Please either summarize this for the net or send me a copy of the replies.
I am really intereted in this myself.

Sincerely

David White

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