counterpoise with LMP2

[uccatvm <uccatvm-: at :-ucl.ac.uk>]

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
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      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
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