High Pressure Physics
The primary effect of high pressure is volume contraction and hence the shortening of interatomic and intermolecular distances. Along with structural modifications are various changes in physical properties such as electric/thermal conductivity, viscosity, melting and magnetic properties. Exploring and understanding the new physical phenomenon under high pressure will open new avenues for designing and synthesizing materials with unique properties.
High pressure chemistry
High pressure chemistry is still a new subject. Pressure can reduce the intermolecular distances which can increase the intermolecular interaction dramatically. When the intramolecular and intermolecular forces are comparable with each other, the system is thermodynamically unstable and the reaction takes place. The high pressure chemical reaction is a solid phase reaction and the reaction path is determined by the crystal structure, which is very different from the one in gas phase and solution.
Super Hard Materials
Super-hard material have gained a lot of interest due to their extensive application in industrial areas, such as the polishing, cutting tools, and hard wear protective coatings. Synthetic diamond and cubic boron nitride are major commercial high pressure materials. Because of the huge commercial application of super-hard material, a lot of attempts have been tried to search and create new super-hard materials. High pressure as one of the fundamental thermodynamic variables can generate the materials with high values of atomic, electron density and high bonding energies which may lead to new super-hard material.
Earth and Planetary Sciences
The composition and evolution of the earth and planets has great influence on the emergence and development of the life. However, information of the earth's deep interior and the planets cannot be accessed directly, since no borehole can be drilled more than twelve kilometer by present techniques, which is far less than the earth's six thousands kilometers radius, not to mention drilling a hole in the planets. The HPSTAR has made great contribution on revealing the detail picture of the deep Earth’s interior. A previously unidentified major phase in the lower mantle, Fe-rich phase with a hexagonal structure was discovered recently. This observation has significant geological implications for enigmatic seismic features beyond ~200 km depth.
High Pressure Technology
A lot of technologies, such as optical spectroscopy, resistivity measurements, and magnetic measurements have been used by scientists in HPSTAR to study the high pressure phenomena. The optical spectroscopy techniques mainly include high pressure Raman spectroscopy, Brillouin scattering, infrared spectroscopy, and optical reflectivity. Electrical resistivity of materials under high pressure can be obtained by four probe electrical measurements in a diamond anvil cell, which is a crucial technique for condensed matter physics research. Magnetic measurements under pressure yield useful information about magnetic moments, magnetic structures and interactions in condensed matter, especially in itinerant electron systems. These high-pressure technologies often combine with extreme temperature condition from low temperatures down to 4.2 K to high temperature up to several thousands K.
High Pressure Synchrotron Sources
Brilliant synchrotron x-rays provide excellent probes for micron-scale samples for a variety of experimental measurements at high pressure. Complex samples at increasingly higher pressures and more extreme temperatures are being studied with higher accuracy probes for characterization of structural, electronic, and phonon properties. The synchrotron techniques including
X-ray diffraction, X-ray total scattering/Pair distribution function, X-ray absorption, Nuclear Resonance scattering, Inelastic x-ray scattering, X-ray image, Raman scattering, Infrared spectroscopy
and Neutron scattering have been used by HPSTAR scientists to probe minute samples at high pressure and many new techniques have been developed.
High pressure nano science
High pressure studies have revealed that the phase transitions, elastic properties and defect-associated deformation mechanisms of materials are domain size dependent. High pressure nano science is a fast emerging field which holds great promise for the discovery of new physics, chemistry and novel properties for applications.
High pressure functional materials
Our research aims to understand how to manipulate functional materials properties and synthesize novel materials with unique functionality using high pressure. High pressure is a promising approach to achieve the highest Tc for superconductor, the highest thermal conductivity, the strongest piezoelectric, thermoelectric effect, etc.
High Pressure Energy
The extreme P-T studies provide a new route towards discovering advanced structural materials and new materials with enhanced performance for energy transformation (i.e. solar, mechanical, chemical to electrical), energy storage (i.e., batteries, capacitors, hydrogen), and energy transmission, sensing and monitoring.