(PDF-4+ 2016, PDF-4/Minerals 2016)
Identification of a two phase fuel cell composition performed using the PDF-4+ program SIeve+. The experimental data are courtesy of the OPAL neutron diffractometer at the Bragg Institute ANSTO, Sydney, Australia.
In 2014, we announced our neutron diffraction analysis capability based on constant wavelength neutron diffraction. In 2015, we added the ability to analyze deuterated materials and continued to produce neutron pattern references for newly discovered materials. Major additions made to the SIeve/SIeve+ analysis programs to quantify and identify materials can be applied to neutron, electron, synchrotron, and X-ray data.
New Capabilities: Time-of-Flight (TOF) Neutron Diffraction Pattern Simulations
Neutron powder diffraction is a useful tool because elemental scattering contrast is quite different when compared to X-rays. Elements in the periodic table often have quite different scattering amplitudes (the scattering cross sections are not strictly proportional to atomic number, Z and isotope).
Unlike standard laboratory X-ray sources, synchrotron sources, nuclear research reactors and pulsed neutron sources are sited at national facilities (available world-wide). One of the initiatives of the ICDD is to expand the content of the PDF-4 to include powder diffraction from facilities outside the X-ray laboratory.
Even though constant wavelength neutron sources continue to be exceedingly productive, pulsed neutron sources continue to be at the technology edge. The basic rationale for this is that current high flux reactors use limiting technology to achieve the power density required to support neutron powder diffraction. The next step is to use extremely intense pulses of polychromatic (white beams) neutrons.
For Release 2016, the PDF-4 software allows users to:
- Import instrument parameters provided by time-of-flight (TOF) neutron facilities (in either GSAS or FullProf formats).
- Simulate TOF neutron powder diffraction patterns using these imported instrument parameters (provided the database entry has atomic coordinates).
- Import raw TOF neutron diffraction patterns (in either d-spacing or TOF units) for visual comparison or full pattern matching to simulated diffraction patterns from the database.
- Perform isotopic substitution for both constant-wavelength (CW) and time-of-flight (TOF) neutron diffraction pattern simulations.
Raw TOF neutron diffraction pattern (La B6) plotted against a PDF-4 simulated diffraction pattern found using full pattern matching.
Full pattern matching results for La B6 using TOF neutron diffraction patterns.
Isotoptic substitution for constant-wavelength (CW) neutron diffraction pattern simulations.