Structure Factor Comparison Program
Rfactor handles many of the functions that are required when two lists of structure factors are compared. It examines two sets of structure factors and finds all reflections which occur in both. It will scale the two data sets to one another, allowing the user to choose between many options. It can calculate the R-value between the two lists, and also generate difference Fourier coefficients and maps of several types. In addition it will generate the function value, gradient, and curvature for the RFACTOR, REALSPACE, ROTATION, and PHASE modules. In refinement it is run in both long and short loops. It can either read the Fc's from a file or calculate them from a map or coordinates.
In the long loop of a refinement cycle Rfactor compares the Fo's and Fc's and determines the parameters of the scaling function. The program also writes out the parameters of the scale function so that they may be read back during the following short loops. It then calculates and writes the function value and gradient for this term. If the curvature is desired RFACTOR will calculate it as well.
In a short loop the parameters of the scaling function will be read from the file produced in the long loop and the crystallographic term's sum will be calculated using those scale factors.
Rfactor calculates the maps used when model building. It can produce Fo-Fc, 2Fo-Fc, 3Fo-2Fc, and Fo-Fo maps in either Ten Eyck MAP format or A. Jones' DSN6 format.