Dear friends,
 I am wondering about the following problem:
 I would like to model - by means of ab-initio calculations -
 the electrostatic effects on a single molecule due to the
 crystalline environment within a molecular crystal, i.e.
 I would like to perform a (possibly high level) calculation
 of a single molecule's electronic structure under the
 influence of a neighbouring molecules' charge distribution.
 An iterative procedure should be necessary to attain
 self-consistency between the ab-initio charge distribution
 of the reference molecule and the neighbouring molecules'
 charge distribution, which will be in turn derived from the
 reference molecule's wavefunction.
 Since I have no deep knowledge of crystallography, I will
 appreciate advises about two issues:
 1) Widely speaking: Is such an approach correct? Can you
    give me some references in the literature? If I have more
    than one molecule (or even different molecular species)
    in the cell a similar approach on more than one molecule
    is still feasible, but is it worth while? How should I
    model the neighbouring molecules' charge distribution
    (Mulliken charges, charges fitted to the molecular
    electrostatic potential, Atom-In-Molecule-derived
    charges, orientable atomic dipoles, ... ) ?
 2) More technically: do you know a program which reads the
    crystalline structure (for example from the Cambridge
    Database) and performs all coordinates manipulation I
    will need ? In particular to obtain cartesian coordinates
    of any specified molecule in the cell surrounded by all the
    neighbouring molecules whose centers of mass are within
    a certain radius from the reference molecule's center of
    mass ?
 Thank you in advance for all suggestions,
  ^^^ | SCALMANI Giovanni                 giovanni #*at*# sg2.csrsrc.mi.cnr.it
  o o | Universita' degli Studi di Milano
   |  | Dipartimento di Chimica Fisica ed Elettrochimica
  \_/ | via C.Golgi, 19                          Phone: ++39-2-26603254
      | 20133 Milano (Italy)                     Fax  : ++39-2-70638129