ON INTEGRATING THE TECHNIQUES OF DIRECT-METHODS WITH ANOMALOUS-DISPERSION .3. ESTIMATION OF 2-WAVELENGTH 2-PHASE STRUCTURE-INVARIANTS

For diffraction data at two wavelengths from a crystal with anomalous scatterers, there are six types of two-phase structure invariants for Friedel pairs. Two of the six are single-wavelength invariants, the ot her four are mixed-wavelength invariants. It is shown that the latter can be estimated by a straightforward extension of results from the pr obabilistic direct-methods theory for the single-wavelength anomalous scattering case described in paper I [Hauptman (1982). Acta Cryst. A38 . 632 641]. Statistical tests of the mixed-wavelength estimates are re ported for small-molecule and macromolecular examples.