Testing Protocols for Obtaining Reliable PDFs from Laboratory x-ray Sources Using PDFgetX3

TL;DR

This paper develops and tests optimized data acquisition and reduction protocols using PDFgetX3 for reliable atomic pair distribution function analysis from laboratory x-ray sources, including modifications for absorption correction.

Contribution

It introduces a variable counting scheme and protocol optimizations for laboratory x-ray PDF analysis, including a new absorption correction method for PDFgetX3.

Findings

Reliable PDFs can be obtained within a few hours of counting.

Optimized protocols improve data quality from laboratory x-ray sources.

Absorption effects can be effectively corrected in PDFgetX3 for high-energy data.

Abstract

In this work, we explored data acquisition protocols and improved data reduction protocols using PDFgetX3 to obtain reliable data for atomic pair distribution function (PDF) analysis from a laboratory-based Mo x-ray source. A variable counting scheme is described that preferentially counts in the high-angle region of the diffraction pattern. The effects on the resulting PDF are studied by varying the overall count time, the use of Soller slits, and limiting the out-of-plane divergence of the incident beam. The protocols are tested using an amorphous silica and a quartz sample. We also present a modification to the current PDFgetX3 data corrections to take care of sample absorption, which was previously neglected in the use of that program for high-energy synchrotron x-ray data. We show that, despite limitations in the Q-range and flux of laboratory instruments, reasonable data for PDF model fits may be obtained using the best protocols in a few hours of counting.