“PC-PDF”: A Search/Display System Utilizing The CD-ROM And The Complete Powder Diffraction File
The Powder Diffraction File (PDF) is a collection of single phase X-ray powder patterns, maintained and distributed by the JCPDS-International Centre for Diffraction Data. Over the past 10 years there has been increasing use of the PDF in computer readable form, but the limited amount of disk space available on most commercial powder diffractometer systems has limited use to a small subset of the total PDF. The recent availability of low-cost Compact Disk Read Only Memory (CD-ROM) systems offers an attractive alternative to conventional disk media. This paper describes a low-cost Personal Computer/CD-ROM system, “PC-PDF”, having a total available storage of 550 Mbytes. While seek times are relatively slow – typically, 0.5 seconds are required to traverse the complete PDF – by use of optimum packing and access algorithms, search strategies based on PDF numbers, chemistry, strongest d-spacing, etc., operate at a speed causing no great inconvenience to the user.