Re: CCL:counterpoise with LMP2

From: Gerd Raether <gerd ( ( at ) ) anterio.com>
Subject: Re: CCL:counterpoise with LMP2
Date: Tue, 14 May 2002 14:28:14 +0200
 Hi Tanja,
 maybe the work of Istvan Mayer et al.
   author = 	 {I. Mayer and \'A. Vib\'ok and G. Hal\'asz and P. Valiron},
   title = 	 {A BSSE-Free SCF Algorithm for Intermolecular
 		  Interactions. III. Generarlization for Three-Body
 		  Systems and for Using Bond Functions},
   journal = 	 {Int. J. Quantum Chem.},
   year = 	 {1996},
   volume =	 {57},
   pages =	 {1049}
 (see also the references there) is useful for you. This approach is
 especially useful if you are going to use small basis sets.  Here you
 also get a BSSE free wave function. Furthermore as far as I know you
 will find also a discussion how the classical Boys Bernardi Method
 should be applied - this should be sufficient if you just go for BSSE
 free energies.
 Gerd
    From: uccatvm <uccatvm ( ( at ) ) ucl.ac.uk>
    Date: Mon, 13 May 2002 21:56:43 +0100 (BST)
    Hi all,
    I am wondering what the most correct way is to do counterpoise with local
    MP2. In the local MP2 method originally proposed by Pulay (Chem.Phys.Lett.
    100, 151, 1983), to each localised MO a subset (orbital domain) of the
    virtual orbitals is assigned.  To calculate the interaction energy of a
    weakly interacting system, the orbital domains of the subsystems are first
    determined at large distance, and used in subsequent dimer calculations at
    smaller intermolecular distances (as recommended in for example Schutz et
 al.,
    J. Phys. Chem. 102, 5997, 1998).
    Now, I assume that (to keep a true counterpoise) it is best to use the
    orbital domains determined at large distance for the monomer+ghost
    calculation. For this, one would first have to determine the domains of the
    monomer+ghost with the ghost at large R, and use the thus obtained orbital
    domains in the monomer+ghost calculation at the smaller distance. What
    do people think? Would this be the correct way of doing it?
    Of course, the BSSE is strongly reduced in LMP2, and should in principle
    be negligible when using an appropriate basis set. However, when using
    small basis sets it may not be negligible, and I would like to know the
    best way of doing counterpoise for these cases.
    Thanks in advance,
    Tanja
    --
      =====================================================================
 	Tanja van Mourik
 	Royal Society University Research Fellow
 	Chemistry Department
 	University College London    phone:    +44 (0)20-7679-4663
 	20 Gordon Street             e-mail:   work: T.vanMourik ( ( at ) ) ucl.ac.uk
 	London WC1H 0AJ, UK                    home: tanja ( ( at ) ) netcomuk.co.uk
 	http://www.chem.ucl.ac.uk/people/vanmourik/index.html
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