TOPAZ: The Single-Crystal Diffractometer at SNS
TOPAZ instrument scientist Christina Hoffmann and scientific associate Matt Frost at TOPAZ.
TOPAZ is an elastic scattering instrument that allows for probing of material structures and responses under controlled environmental conditions. It enables neutron measurement of the same single-crystal samples that is possible with x-ray diffraction.
Data are collected on samples of 0.1 mm3 or less. Resolution is such that an average unit cell size of [50 × 50 × 50] Å3 for compounds of moderate complexity can be easily accommodated. This includes inorganic large and porous framework and guest-host materials, metal (in-)organic cluster and molecular compounds, and organic arrangements of interest for biology and medical applications.
View inside the sample enclosure: in front are the interchangeable focusing optics within 2 m upstream of the sample. This allows focusing between an area of 0.1 × 0.1 mm and 3 × 3 mm. The fully populated detector array with sample loading from the top encloses the sample position spherically.
Materials investigated with TOPAZ include functional materials of the high Tc superconductor perovskite structure family, magnetic superstructures in perovskites, and spinels. Also of importance are catalytic precursors, metalhydride materials for potential hydrogen storage applications, and organometallics. Potential future studies include high-density, three-dimensional storage materials, known as single molecule magnets. These materials have raised much interest but in the past could mostly be studied only in polycrystalline samples using neutron diffraction.
Neutron single-crystal diffraction is uniquely positioned to decipher the pathways and bonding of hydrogen in the presence of heavy metal ions as it is sensitive to both classes of elements in comparable quantity. Simultaneously, the magnetic ordering and structure can be investigated exploring the fact the neutrons carry a magnetic moment. This allows for investigation of magnetic and spin density studies in magnetically interesting materials.