Subject: Re: CCL:van der Waals parameters from ab initio calc?

From: [email-masked] (Joerg Hill)
Date: Tue, 24 Jan 1995 13:32:20 -0800

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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From: [email-masked] (David J. States)
Date: Tue, 24 Jan 1995 20:24:52 -0600

|> 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