Neutron Scattering Group - January 1995
The Neutron Scattering Group is one of a number of groups at the Australian Nuclear Science and Technology Organisation’s Lucas Heights Research Laboratories which is carrying out crystallographic research, or research heavily dependent on crystallography and crystallographic techniques. The Neutron Scattering Group (Dr Chris Howard), making use of neutron beams from the HIFAR research reactor, is in fact within the same program (Applications of Nuclear Physics) as the team led by Dr Richard Garrett, responsible for operating the Australian National Beamline Facility at the Photon Factory, Tsukuba, Japan. Crystallographic studies are undertaken within the Advanced Materials, Biomedicine and Health, and Environmental Science programs - these will be reviewed at a later date.
The specific role of the Neutron Scattering Group is to carry out scientific research making use of the thermal neutron beams from the HIFAR reactor. Most of this research involves collaboration with other institutions, especially Australian universities.
Single crystal studies are conducted under the charge of Dr Lindsay Davis. There are two four-circle diffractometers for single crystal work, 2TanA and 2TanB. The 2TanA diffractometer has the higher resolution, and this diffractometer has also been completely rebuilt during 1994. The new 2TanA is a Huber four-circle instrument, controlled by a PC-486 with locally developed Windows based software, and equipped with a cryorefrigerator (to 10 K). A furnace, for studies to 1000oC, is to be ordered shortly. Computer programs XTAL3.2, SHELXS and SHELX92 are available for data reduction and analysis. The instrument is used for classical neutron crystallography, such as the location of hydrogen atoms in complex crystal structures. A recent example, of work completed on the old 2TanA, is the elucidation of the role of hydrogen bonding in the formation of complexes between benzoic acids and cyclam (collaboration with Professor Len Lindoy and his team at JCUNQ).
There is a strong program in powder diffraction. The instrumentation at present comprises the high resolution powder diffractometer (HRPD) which is the responsibility of Dr Brett Hunter, and the medium resolution powder diffractometer (MRPD) being run by Dr Shane Kennedy. The HRPD is used for the study of more complex crystal structures, or high precision crystallography, whereas the MRPD tends to be used for phase transitions, magnetic structures, and time-resolved crystallographic investigations. Samples can be cooled (to 4 K), heated (to 1700oC), or held under pressure during the measurements. As regards the applications of powder diffraction, special interests of the group include high critical temperature superconducting oxides and related materials (Brett Hunter and Dr Michael James, in collaboration with staff at the Argonne National Laboratory and Cambridge University respectively), fast ion conductors (Lindsay Davis, working with Ron Balsys at the University of Central Queensland, and New Zealand scientists), zirconia and zirconia based ceramics (Chris Howard and Dr Margaret Elcombe, working with Drs Ray Withers and John Thompson at the Australian National University, Drs Steve Hull and Ron Smith at the Rutherford Appleton Laboratory, Dr Richard Hannink and his co-workers at the CSIRO Division of Materials Science and Technology, Dr Erich Kisi at the University of Newcastle, and ICI Advanced Ceramics), metal hydrides (Margaret Elcombe and Shane Kennedy, with Drs Evan Gray and Erdong Wu at Griffith University, Dr Stewart Campbell at the Australian Defence Forces Academy, Dr Brendan Kennedy at the University of Sydney, and Erich Kisi), and magnetic structures and phase transitions (Lindsay Davis with staff from CSIRO Applied Physics; Shane Kennedy, with teams from the Monash University magnetism group led by Dr Trevor Hicks, Dr Peter Goodman and co-workers at the University of Melbourne, Dr Tim St Pierre at Murdoch University, and Stewart Campbell). The applications of neutron powder diffraction are supported by considerable in-house expertise in various methods for data analysis, including powder pattern indexing (Visser program), structure determination, and structure refinement by the Rietveld method (GSAS and LHPM). This expertise includes some familiarity with the construction of electron/nuclear density maps from X-ray/neutron powder data by the maximum entropy method. Complementary studies by X-ray powder diffraction (exploiting the access to the Photon Factory) and neutron powder diffraction are another current interest.
The neutron scattering group maintains further instrumentation, serving those with interests in what are perhaps more specialised areas of crystallography. This includes the triple axis spectrometer (Margaret Elcombe) for studies of excitations in crystalline solids, the long wavelength polarised neutron polarisation analysis instrument, Longpol, (Shane Kennedy) which is used for basic studies in magnetism and more recently for the investigation of magnetic flux pinning in superconductors and measurements on magnetic ribbons, and the small angle neutron scattering instrument, AUSANS, (Dr Robert Knott), now being commissioned. In addition, members of the group (Margaret Elcombe, Michael James) are assisting with the commissioning and operation of the new SURF neutron reflectometer at the ISIS facility, Rutherford Appleton Laboratory, U.K.
Members of academic institutions which subscribe to the Australian Institute of Nuclear Science and Engineering (AINSE) are reminded that they are eligible to apply for instrument time on the neutron scattering facilities. Enquiries should be addressed to Dr Roger Gammon, the AINSE Executive Officer (email@example.com) - the closing date for applications is September 30th. Access for collaborative research on topics of mutual interest is another option - enquiries about such access should be made directly to ANSTO Neutron Scattering Staff.