Abstract
The indexing process, that is determination of unit-cell parameters, is the first important stage of the crystal structure determination from powder diffraction data (SDPD). Accurate Bragg positions (2θ or d values) of 10∼20 peaks picked up by peak-search from low 2θ angle side are indispensable for determination of lattice constants with hkl indices. Subsequently, space group can be estimated according to systematic absences based on obtained lattice constants. Integral intensities of each reflection are tentatively extracted by the whole powder pattern fitting i.e. the Le Bail or Pawley methods. Crystal structure of small organic molecule can be solved by the direct method or the charge flipping algorithm. In this report, the brief summary about indexing and whole pattern fitting was described. Furthermore, some practical examples of SDPD of small organic molecules by the direct method (EXPO2009) and the charge flipping (Superflip) were demonstrated.
