Neutron diffraction is a powerful technique to clarify the relationship between the crystal structures and the properties of functional materials. Since neutron atomic scattering factors do not depend on atomic numbers, neutron diffraction gives more reliable structural information than X-ray to detect light elements among heavy ones. In 2007, the proton accelerator project, J-PARC, will be completed and start delivering the most intense pulsed neutron in the world. Instrument proposals are being reviewed in the viewpoint of science, instrumental designs, and manpower, etc. This article was written to introduce the technique of pulsed neutron powder diffraction to promote high-pressure science in J-PARC.
This article has reported several inelastic neutron scattering experiments under pressure. A significant change of elementary excitation energy such as phonon and magnon can be observed associated with pressure-induced phase transition in some materials. In such a case, a direct information on atomic interactions driving the phase transition can be obtained.
J-PARC project is under construction in Tokai village to be completed by 2007 with collaboration between JAERI and KEK. This project contains a neutron science facility (JSNS), which will give us two order of magnitude higher neutron flux compared to the existing facilities. JSNS will give opportunities not only on innovative scientific development for academia but also on new engineering use for industries. This article will present a brief description of the present status of JSNS and neutron instruments.
In this article, I tried to discuss what kind of science could be targeted by the combination of neutron elastic scattering and high pressure devices. Construction of a user facility providing intense pulsed neutron is now in progress in Japan Proton Accelerator Research Complex (J-PARC), Tokai, Ibaraki, Japan. Since we are eager to obtain a beam line dedicated for high pressure sciences in the exciting facility, I reviewed what kind of science in the high pressure world has been already performed by neutron elastic scattering technique in order to think about its new application to high pressure sciences.
A retrospective description is made of a program for launching high-pressure neutron scattering experiment, basically for the first time in Japan. Materials, design, and operation of various high-pressure cells developed are presented chronologically. Results obtained from experiments using such cells involve phonon dispersion relations of RbCl, Néel temperature of fcc Fe, and magnetic structures of rare-earths.
At present, neutron diffraction experiments at high pressure up to 20 GPa are available only at a spallation neutron source in ISIS, Rutherford Appleton Laboratory, UK. Experimental procedures and techniques for measuring neutron diffraction at high pressure are reviewed in this article. In addition, recent achievements on structural determinations of hydrogen-bearing materials at high pressure are reviewed.
This article addresses the design of a high-pressure and high-temperature apparatus that is to be installed in the Materials and Life Science Facility of the J-PARC. Recent advances and problems of in-situ neutron-diffraction experiments under pressure are reviewed focusing on the technical aspects. A conceptual design of a high-pressure press dedicated to the new generation neutron facility is proposed.
In this article, development of Kawai-type of high-pressure apparatus is described. Versatile application of this apparatus to solid Earth science is demonstrated by elucidating the characteristics of the 660 km discontinuity and formation of the lower mantle. Recently the maximum attainable pressure in Kawai-type apparatus has been extended to 63 GPa by adopting sintered diamond as the anvil material. Therefore, phase equilibrium and melting experiments of Earth materials have been carried out to conditions deep into the lower mantle. The results will substantially advance our understanding of the structure and evolution of the Earth.
This article shows the recent Raman studies for type I silicon clathrates doped with Ba, K, and I atoms under high pressure at room temperature. The obtained Raman spectra indicate vibrational signals related with guest atoms encaged in the Si cages in a frequency region lower than 100 cm-1. In order to explore the pressure-induced phase transition, the Raman spectra were measured for the Si clathrates under high pressures using a diamond anvil cell. The spectral changes associated with the phase transition were observed, and the mechanisms of the phase transition were discussed on the basis of the spectral changes.
Theoretical study of mineral physics has rapidly progressed by first principles method based on the density functional theory. In this article, recent studies of the Earth's constituents and related materials by means of the first principles electronic structure calculation methods are reviewed. Especially, calculations of high-pressure thermodynamic properties, PVT equations of state, high-pressure elasticity, high-PT phase stability are reported. These techniques are applied to study thermochemical state and physical properties of the Earth's lower mantle.
At the National Metrology Institute of Japan (NMIJ/AIST), national pressure standards are developed and maintained. In this article, the pressure standards, calibration services and activities for ensuring the reliability of the standards are described. A traceability system of the calibration services and the mutual recognition of national measurement standards are also outlined.