Patterson-oriented automatic structure determination: getting a good start

On the basis of a generalized symmetry minimum function several computer-oriented methods for interpreting Patterson functions and for locating the position of heavy-atom fragments in crystals belonging to space groups of higher symmetry than P1 have been developed. The methods utilize cross vectors for finding relationships among the peaks of the symmetry minimum function. This approach has the advantage of suppressing false peaks of the symmetry minimum function, in locating more than one atom and in revealing the correct solution with greater probability. The heavy-atom fragment can be extended by superposition or Fourier methods. The methods are valid for all space groups, are simple to apply and form the basis for fully automated structure determination. In contrast to many other Patterson methods no a priori structural information is necessary. A few selected examples demonstrate the power of the new version of the computer program XFPS.