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THE USE OF A FREQUENCY CHECK IN THE VECTOR VERIFICATION METHOD.
PRINCETON UNIV N J
The frequency check, utilizing three-dimensional superpositions of the Patterson and vector verification maps, assigns relative values to positions in electron-density space which are consistent with both the Patterson function and the space group symmetry of the crystal system. These relative values-which represent the extent of peak coincidence between a Patterson and electron-density function-facilitate the choice of the first tentative atom position, a decisive factor in the success of the vector verification procedure. Employing a bivalued Patterson map, each three-dimensional superposition resulting in a relative value requires one to five seconds on a large solid state computer. Author
Pub. in Acta Crystallographica (Denmark) v17 pt12 p1599-1603 Dec 1964 (Copies available only to DDC users).