Computer Prediction of Organic Crystal Structures Using Partial X-ray Diffraction Data

This paper describes a computational procedure for the
determination of complete crystal structures when
the cell dimensions and space group only are known from X-ray
crystallography. Molecular structure and conformation
are assumed, and cannot be refined. When diffraction intensity
data are available, the procedure offers an alternative
to standard methods for the solution of the phase problem. The
procedure applies to a wide range of organic molecules
thanks to the evolution of the force field and of the computer
programs. While the full ab initio prediction of
crystal
structures is still, in our opinion, a faraway goal, an important and
fruitful application of this kind of computer
modeling is in the completion of partial X-ray determinations when
single crystals of suitable quality are not available,
a rather frequent occurrence. Examples of this application are
given, and its success implies that the need for producing
good quality single crystals of newly synthesized organic compounds is
nowadays less stringent, especially when
only a knowledge of the intermolecular organization pattern in the
crystal is sought.