A Qualitative and Quantitative PC program for X-ray powder diffraction
FARHAN program (1998) can efficiently provide precise qualitative and quantitative results from X-ray powder diffraction data of unknown sample comprises of several crystalline phases of any type, in one program run, even without user intervention. In favourite cases, the complete qualitative and quantitative results can be obtained by the following three steps: (1) Select the fully-automatic identification and quantification option. (2) Input the sample file name. (3) Input the standards file name.
The program has special adjustable Search-Match-Identification (S-M-I) parameters for dealing with very problematic sample i.e. sample severely suffer of preferred orientation and/or solid solution. Furthermore, the author has implemented new powerful matching routine which uses variable Intensity Error Window (IEW) and a tuneable combined figure-of-merit (FOM), which makes the program’s automatic identification procedure succeed in most cases. Whether automatic identification was successful or not the program provides the user with many FOM’s and dynamic testing functions which help him correctly selecting the present phases in the sample. However, for comparison with other Search-Match programs or for use in some special cases, matching routine with fixed IEW is also included in the program.
The addition of quantitative analysis to the S-M-I procedure is new and of practical importance in many areas such as in materials quality control, mineralogical surveys, and in most research projects and analysis problems in which the XRPD is used as a primary tool. In FARHAN the most widely used and well-documented internal standard quantification method in its generalised form (via RIR) has been implemented. Thus, the analyst can use any diffraction line or multiple lines to quantify the found phases. The default program’s quantification routine (APR) is based on the Adiabatic Principle method (Chung, 1974b). Where no internal standard needs to be added to the sample. However, in the cases where amorphous phase is expected to present or an unidentified or identified phase with unknown RIR is present, the program’s Matrix-Flushing routine (MFR) (Chung, 1974a) should be used, where the amorphous content can be estimated. Phases quantification from XRPD data using FARHAN program has never been easier. Using APR the analyst dose not need to perform any special action. While, with the MFR the analyst may need to advise the program which one of the found phases is the added standard, and its weight percent. Then, on the analyst’s request, the program calculates the weight percent concentration of the found phases either before or after the addition of the standard to the sample
Also, included in the program many identification and education supporting routines such as internal-standard line positions correction routine, quantitative multiphase simulated diffractogram routine, 2q-I or d-I diffractogram editing and manipulating routine, user data base creation and expansion routine, and other utility routines.
At the strategically steps, special effort has been paid to allow the program to either performs a smart selection or protecting the user from inputting wrong value.
The way in which the program has been developed allows the professional diffractionest to fully utilise his knowledge. While it can easily and understandably be used by inexperienced analyst and student as to helping them to master the identification subject. On the other hand, it can help the instructor to put examples and exercises to teach his students, in very efficient way, the different techniques used in tackling different frequently encountered identification problems caused by systematic errors, solid solution, preferred orientation, lines overlaping in multiphase sample, etc. .
The most important theoretical backgrounds of the program have been published in the Powder Diffraction 14.1, 16-21, 1999 (journal).