Computer Automation of X-Ray Powder Diffraction

Abstract

The interfacing of a Hewlett-Packard 9825 calculator to an Enraf-Nonius microdensitometer and a Philips powder diffractometer provides automated data collection and manipulation on a routine basis. Data is acquired and stored on a floppy disk; background corrections are made; diffraction peak maxima are found, normalized and plotted; a table of approximate d-spacing (±0.0lÅ) is printed. The analyst designates the internal standard peaks. Corrected d-spacings are then computed, tabulated and printed above the appropriate peak. An accurate d-spacing scale is drawn on the plot. The total time for a scan is approximately twenty minutes with only about five minutes of operator time required. The program is conversational and requires little prior knowledge of the software by the operator. Data interpretation is further aided by supporting programs to calculate patterns from literature, determine lattice constants for observed phases, help index patterns, deconvolute overlapping peaks, carry out crystalline size determinations and perform search/match procedures. Such supporting programs are possible because, even though the system can be used in a “dedicated” manner, it is still a stand-alone computer. Thus, the desired degree of automation in data collection has been obtained without sacrificing flexibility.