The additional four points in the higher angle area are determined so that they follow the trend of the background line in the lower angle area, and keep smoothness of the background function. More precise determination was precluded by the fact that too many overlappings in the higher angle area make it impossible to decide where a background point should be positioned. Although, there is a short region in the higher angle area (123.65° to 124.50° approximately) in which overlappings are not too heavy, and it was used as a guidance for correction of the positions of the additional background points.

The background function was corrected several times during the first two refinements (in lower angle area, as well as in higher).

The background (red squares) and the pattern can be seen together and compared in one of the figures which ilustrate results of following refinements:

• Refinement with the group Pbnm in the lower angle area
  
• Refinement with the group Pbnm in the whole range of data
  
• Refinement with the group P2₁/a
  
• Refinement with the group P2₁/n
  

Remark: Rietica's grafic program always shows experimental data with unconnected black crosses, calculated profile with a red line, indices with blue bars, and the difference plot with a green line.

General Remarks

Program used was Rietica, PC-version. In all the following refinements starting values in the program were set as listed:

• dumping factors all set to 0.90
• peak shape chosen: Pseudo-Voigt (FCJ Asym)
• starting scale factor: 1.0000
• starting B values for all atoms: 0.6
• zero correction: 0.0000
• values for the resolution function parameters: U=0.05°², V=-0.15°², W=0.20°²