The reliability indexR2as a versatile tool in structure analysis of inorganic and small molecular compounds

Abstract

Applications of R_2 in small-molecule crystallography are described. Ways of using R_2 to evaluate initial models of a structure are discussed. These models, obtained from Patterson methods, are usually small. They may include one or more heavy atoms and pseudosymmetry is sometimes present in the model. The R_2 criterion is used also to identify misplaced atoms prior to the start of the expansion process. Finally, R_2 is used during structure expansion by the application of phase refinement or Fourier methods. Details of the procedures of extension, as well as the role of R_2 therein, are presented and evaluated. Results obtained with various test structures are discussed.