New neutron sources and new instrumentation are being developed to satisfy this demand, and promise to significantly increase the number of single-crystal neutron diffraction studies in the near future. Nevertheless, the demand for neutron diffraction resources is growing and exceeds their availability. Single-crystal neutron diffraction studies constitute a small percentage (2%) of the total number of diffraction studies, largely because of the limited availability of neutron facilities and the requirement of much larger crystals as compared to X-ray studies. A 4 K closed-cycle helium refrigerator is permanently mounted on the χ-circle of the goniometer to provide temperature control between 4 and 450 K.
#Ornl single crystal diffraction software
a modified version of the SPICE software package. In addition to the traditional step-scanning mode, a more efficient continuous-scanning mode was developed, and both these are implemented through a LabView-based control program, i.e. Given these effects, the monochromator bending can be adjusted to deliver high intensity primarily for crystal structure refinements or high resolution for resolving symmetry changes. The ω-scan peak width increases with monochromator curvature and this width versus scattering angle flattens. The flux increases because the lattice strain in the silicon crystals increases. With increased bending of the monochromator, the incident flux on the sample passes through a maximum, increasing by ×2.0 for 1.000 Å, by ×3.5 for 1.536 Å and by ×3.5 for 2.540 Å, as compared to the flat condition. Either high-resolution or high-intensity modes are possible by horizontal bending of the monochromator. The instrument is well suited to studies of nuclear and magnetic structures as a function of composition and temperature, resolving symmetry changes (lattice distortions and local structural changes), mapping the evolution of complex magnetic phases, determining hydrogen bonding, analyzing nuclear and spin densities, mapping diffuse scattering, and exploring fiber diffraction. A four-circle neutron diffractometer with a new multi-wafer 331 Si monochromator has been installed and commissioned on a thermal beamline at the High Flux Isotope Reactor at Oak Ridge National Laboratory.
0 kommentar(er)
