INTEGRATION OF PATTERSON INFORMATION INTO DIRECT METHODS .2. THE 1ST APPLICATIONS

A probabilistic formula [Giacovazzo (1991). Acta Cryst. A47, 256-263] estimates triplet invariant phases given prior information on a non-Harker Patterson peak u. The formula requires prior information both on the coordinates of the peak and on the scattering factors of the atoms with mutual distance u. Since this second type of information is usually not available, the formula has been modified so that it depends on u and on the Patterson peak intensity in u. Some applications are described. The use of some algebraic relationships among structure factors arising from the positivity and atomicity of the electron density function are also considered.