PDWIN-WINDOWS PROGRAM PACKAGE FOR X-RAY POLYCRISTAL ANALYSIS

I.G. Ivanov, N.N. Popudribko, N.G. Pjatygina, V.A. Firsova, V.S. Fundamensky

Bourevestnik,Inc. 68 Malookhtinskij ave., St.Petersburg 195272 Russia
FUND@XRAYLAB.SPB.SU

Keywords: qualitative analysis quantitative analysis, 2q corrections, data reduction, powder diffraction file

The authors have developed the first part of the software package for the phase analysis PDWin. The current version includes the following programs

• Data Reduction
• 2q Corrections for Internal and External Standards
• Work with the Powder Diffraction File
• Qualitative Analysis
• Quantitative Analysis

The Data Reduction program is intended for background subtraction and calculation of the diffraction line characteristics such as line position, center of gravity, area and FWHM. The background is approximated by a polynomial which degree is determined by a user in the range from 1 to 7. Peak intervals are calculated by the first and the second smoothed derivatives. After that the program passes to the profile parameter's refinement with the help of a non-linear least -squares method. The raw data observed profiles are fitted to the doublet asymmetry pseudo-Voight functions. Refined parameters are divided into two categories:

1. Always refined parameters such as angle position of the peak maximum and its intensity.

2. Parameters included or not included into the refinement procedure by a user. They are FWHM, asymmetry, form factor, a₂ shift from a₁ and their intensity's ratio.

The program working with the Powder Diffraction File builds the sub-files in accordance with user criteria's. The newly formed file can serve as an initial one for building the other sub-files etc. In the first version of the program the initial file and derivative files are saved in the PDF-2 format. The cards of both the initial file and the derivative file are possible to look through in graphics.

Criteria's of sub-files forming:

• Card numbers, intervals and individual numbers
• Compounds names, their fragments and combinations
• Crystal systems and their combinations
• Quality max and their combinations
• File sub-file names (for instance: minerals, cements, etc.) and their combinations
• Chemical elements. Any chemical elements in the periodical table can be determined as an allowed, prohibited or possible. A group of prohibited or allowed elements can be determined too.

All the mentioned above criteria's can be combined with unification or intersection.

In the second version of the software package the initial file is transformed into the file in database format. Working with this data file a user can add his own standards into the base, unit several subbases, making inquaries on criteria's which use all the base information.

The Qualitative Analysis program works with file containing the peaks angle characteristics in the format of the Data Reduction Program output file.The Search procedure is the first part of the program. It uses two keys: the accuracy limit of 2q values and the number of the lines of the sample that coincide with the strongest lines of the standard. This procedure generates the card list satisfying the user demand. If the user is satisfied with the list the Match procedure begins to work. The first one describes a fraction of coincided lines among the total lines quality, the second one users lines intensity. The card list is the result of matching. The final procedure calculates the concentrations of the founded cards and makes the model sample.

The Quantitative Phase Analysis program realizes three methods.

• The total analysis of multiphase mixture
• The analysis of n-component system
• The analysis of the sample with known mass absorption coefficient (MAC)

The first method uses any number of the lines of the sample to calculate concentrations. The lines of deferent phases can overlay. The samples of pure phases are needed for calibration. The second method permits to analyze several samples of the same phase content simultaneously without pure phase samples. The third method can be used to calculate concentration of any one phase in the sample without other phase's concentration determination. The presence of pure phase or standard samples with the same phase content as the sample is necessary.

The programs are written in Visual Basic 5 and work under Windows 3.1/95/NT. The programs have build-in Help system and are accompanied by well-illustrated documents. Friendly and intuitively clear interface makes work with the package easy and pleasant.