The command 'read stru' allows the user to read a DISCUS
type structure from the file <file>. Note that some DISCUS
keywords and the use of molecules are not supported by
PDFFIT. To read structural information for multiple phases
simply repeat the 'read' command. In order to discard
the current structure use the command -> 'reset'. Note that
DISCUS only supports an isotropic temperature factor B.
When reading a DISCUS structure the temperature factor is
converted according to: <u(ii)> = Bglm-1/(8pi**2al*am*).
PDFFIT automatically recognizes the structure file format
of the input file !
"n" | "x"
,<qmax>,<qsig>,<file>
The command 'read data' reads the observed PDF. The file
format is ASCII and contains 'r G(r) dummy dG(r)' in each line.
The value of 'r' is in A, G(r) is the reduced PDF. The
third column is ignored (needed for KUPLOT) and the last
value 'dG' is the error of the PDF used to calculate the
weight (w=1/dg**2) for this point to be used for the
refinement. Additional to the filename <file> the commands
needs the following parameters: First the type of radiation
is specified, "n" stands for neutrons and "x" for X-rays.
Next the maximum value of Q <qmax> is given followed by the
value of <qsig> defining the Q resolution. To read multiple
data sets just repeat the 'read' command.
"n" | "x",<qmax>,<qsig>,<file>,<rfile>
This command is similar to 'read data' but rather than reading
a PDF, a difference PDF is read from file <file>. The format
is identical to the PDF file format. The additional parameter
<rfile> specifies a reference PDF, so that the model PDF fitted
to the read data becomes CALC - REFERENCE. See Users Guide for
more details.