The flowchart below color codes the three main stages of the structure determination process. A brief description of each part of the process can be obtained by clicking on that particular component on the flow chart. The actions that occur in each stage:
are described in the summaries that follow.
The sequence coded in red represents the refinement stage of the structure determination process. Here the model developed in the solution stage is developed in full through successive cycles of refinement. In each cycle a model for the structure, given in a "name.ins" file, is input with the X-ray data file, "name.hkl", into a least-squares refinement program. The refinement program tries to adjust the parameters of the model to give the best agreement between X-ray data calculated from the model and the observed X-ray data and then calculates an electron-density difference map that can be used to identify missing atoms or other problems in the structural model. The refined model parameters and difference map peaks are output to a results file, "name.res". This results file is then examined using a graphical display program and or a text editor, improvements to the model are added, a new input "name.ins" file is prepared, and the refinement cycle starts anew.
Once all available improvements to the model have been made and the refinement has converged, i.e. structure parameters now vary only slightly between succesive refinement cycles, the structure determination is complete. At this point three different types of files are output and these are coded in tan on the flowchart.
The components enclosed in the aqua colored box are the heart of the structure determination process and the comuter programs included in the box represent the very miniumum needed to put together an effective crystallography software package.
Go to clickable structure determination flowchart
Go to Structure Determination Software Page
Last modified December 18, 1996