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人氣1335
SIKA1 - Neutron Science | 2014-10-22 04:00:26 ~ 2021-05-17 15:14:24

 

National Cheng Kung University 
December 4-6 th  2014

The NSRRC and NCKU will host a meeting on inelastic scattering to promote the use of the cold triple axis, SIKA in Taiwan.

Over the three-day meeting invited speakers will give talks on how neutrons can measure phonons and magnons in condensed matter. These results help in the understanding of magnetic coupling, heat transport and structural distortions within samles for example.

Organizers:

Lieh-Jeng Chang, NCKU

Jason Gardner, NSRRC

Contact E-mail:

neutron@nsrrc.org.tw

 

 

人氣1239
SIKA1 - Neutron Science | 2014-05-26 16:48:16 ~ 2021-05-17 15:15:00

 

Figure. A Chinese puzzle ball consisting of decrative concentric spheres.

Two isostructural and concentric clusters [Cu28(H)15(S2CNR)12]PF6 (NR=NnPr2, aza-15-crown-5) are air- and moisture stable and were prepared through a one pot synthesis.  Researchers from National Dong Hwa University, in collaboration with scientists from Australia and France used a combination of neutron and X-ray diffraction and NMR to determine the structure of this rhombicuboctahedral copper polyhydride complex.  The onion-like structure displays a geometric entity that is reminiscent of a Chinese puzzle ball was characterised on the KOALA diffractometer by measuring over 57,000 reflections.  The presence of capping, truncating, and interstitial hydrides within the metal framework was modeled and reproduced by density functional theory (DFT) calculations.  The core of each copper hydride nanoparticle comprises one central interstitial hydride and eight hydrides that cap the outer triangular faces. A further six truncating hydrides form an unprecedented bridge between the inner and outer copper atom arrays. The irregular inner Cu4 tetrahedron is encapsulated within the Cu24 rhombicuboctahedral cage, which is further enclosed by an array of twelve dithiocarbamate ligands that subtends the truncated octahedron of 24 sulfur atoms, which is concentric with the Cu24 rhombicuboctahedron and Cu4 tetrahedron about the innermost hydride. This Shape, within a shape is reminiscent of ancient Chinese puzzle balls.

Figure. Highlighted on the front cover (DOI:10.1002/anie.201405105)

Alison J. Edwards, Rajendra S. Dhayal, Ping-Kuei Liao, Jian-Hong Liao, Ming-Hsi Chiang,

Ross O. Piltz, Samia Kahlal, Jean-Yves Saillard, and C. W. Liu*

E-mail: chenwei@mail.ndhu.edu.tw

A research team including scientists from the National Synchrotron Radiation Research Center (NSRRC) has recently measured he low temperature magnetic susceptibility of three Yb3+ cubic pyrochlores and observed a crossover from antiferromagnetic to ferromagnetic ordering as the lattice increases.  These results demonstrated that the application of chemical pressure through the series of Yb-pyrochlores efficiently perturb the fragile quantum spin fluctuations of the Yb3+ ions.  They also highlight the close proximity of Yb2Ti2O7 to a quantum instability, which may explain the current debate in the literature about its exact ground state.

The unit cell of the pyrochlore lattice where the metal ions can create independent, frustrated sublattices of corner sharing tetrahedral.

Bulk properties of Yb2Ge2O7 produced under high pressure and high temperature.  

人氣738
SIKA1 - Neutron Science | 2014-01-13 20:28:39 ~ 2021-05-17 15:15:00

The SIKA cold-neutron 3-axis spectrometer, which is operated by the NSRRC, has taken its first neutron scattering patterns.  A diffraction pattern of a common standard Ni was first measured in diffraction mode before the 3rd axis was added to produce an inelastic neutron scattering spectrum of a crystal-field excitation in PrFeO3

A fixed incident energy of 5.11 meV was used and the spectrum shows a scan of the final energy, with the excitation at an energy transfer of around 2 meV. 

SIKA is now working towards getting a full operating license from the regulators and expects users to apply for beam time in the September 2014 call for proposals.

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