Chemistry Reference
In-Depth Information
DATA TREATMENT
6.1
INTRODUCTION
Two-dimensional X-ray diffraction patterns contain abundant information for various
applications. To accurately interpret and analyze 2D patterns it is necessary to apply
some data treatment processes [1-4]. Most data treatment processes can be categorized
into one of the following four purposes. Some data treatments are to eliminate or reduce
errors caused by detector defects, such as corrections for nonuniform detector
efficiency and corrections for geometrical distortion. Some data treatments are to
remove undesirable effects of instrument and sample geometry, such as corrections for
polarization, sample geometry, and absorption. To analyze the 2D diffraction pattern
for applications that are long established before area detectors were available, some-
times it is necessary to transfer the 2D frame into a format such that the data can be
presented or further analyzed by conventional means and software. For example, when
2D frames are used for phase identification, the first step is to integrate the frames into
one-dimensional diffraction profiles. Then, the diffraction profiles can be used to
search andmatchwith the ICDDPDF database [5-10]. Some treatments, such as frame
smoothing, are for cosmetic reasons and mainly used for reports and publications.
6.2 NONUNIFORM RESPONSE CORRECTION
An area detector can be considered an array of point detectors. Each pixel has its own
detector counting curve. The detector counting curve represents the quantum
