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since Jan 2006

 
Our research involves interdisciplinary frontier areas in physical chemistry, inorganic chemistry, chemical physics and materials science, specialized in molecular spectroscopy and application of synchrotron techniques. In particular, chemistry and materials development under extreme conditions, i.e., at high pressures and/or extremely low or high temperatures far beyond ambient condition, is the theme of our research program. The following are some fundamentals.
 
Why high pressures?
EarthPressure constitutes one of three fundamental thermodynamic parameters in chemistry, spanning some 60 orders of magnitude in the universe. Application of high pressure to matter significantly alters the interatomic distances, and thus, influences the nature of intermolecular interactions, chemical bonding, molecular configurations, crystal structures and stability of materials. Extreme pressure can even induce transformations involving the strongest chemical interactions that exceed 10 eV (965 kJ mol-1) such that chemical bonds and even the well known properties of elements and compounds can be completely changed. Therefore, studies of materials under conditions far beyond ambient, such as at very high pressures, represent a research frontier with great fundamental and applied significance in chemistry, physics, biology and earth sciences.

What happens under extreme pressure conditions?
CompressionGases and liquids not only solidify under pressures, but they can be converted to metals and even superconductors. Many simple molecules exhibit wealthy high-pressure phenomena associated with novel molecular and electronic structures with profound implications.  For example, the very simple water molecule exhibits a surprisingly sophisticated phase diagram in the high pressure regime. Many fundamental chemical questions involving hydrogen bonding, ionization, and proton/electron transfers as well as formation of novel structures become prominent in that domain. One of the most significant discoveries of water is the binding capacity with hydrogen under high pressures and low temperatures, which immediately shed light on the hydrogen storage issues important for next generation clean fuels. For another example, the triple bond in diatomic nitrogen molecule, which is among the strongest chemical interactions in nature, is weakened by pressure and subject to breaking under extreme conditions. As a result, a novel singly-bonded nitrogen has been synthesized under ultra-high pressures and temperatures, opening a promising avenue to search high energy density materials.
 
How to achieve extreme conditions?
DACDiamond anvil cell (DAC) is a fundamental apparatus to achieve static high pressures (up to several million atmospheres). The accelerating developments in DAC techniques over the last decade have enabled observations of extraordinary phenomena on materials under extreme conditions. To achieve extreme temperatures, we use either infrared laser heating or resistive heating method which is capable of reaching several thousand Kelvins, and cryogenic stations to reach down to several Kelvins.
 
What probes are available for characterization of novel structures formed under extreme conditions?
CLSMaterials loaded in a great variety of DACs allow the use of Raman scattering and infrared spectroscopy to examine the vibrational structures in a broad temperature, pressure, and spectral range. The availability of 2nd and 3rd generation synchrotron radiation facilities, which provide extremely high photon flux and brilliance tunable over a broad energy range, has greatly facilitated in situ investigation of novel structures formed under pressures.
What are the current research projects in our group?
Diamond
Pressure tuning of 1D nanostructured materials
Diamond
Hydrogen storage materials
Diamond
Porous materials (e.g., metal-organic frameworks - MOFs)
Diamond
High energy density materials
Diamond
High-pressure photochemistry
 
References:
Y. Song, Phys. Chem. Chem. Phys. 15,14524 (2013).
Y. Song and M.R. Manaa, J. Phys. Chem. C, 116, 2059 (2012).
Y. Song and Z. Dong, in ˇ°Nanowiresˇ±, p527-552, ed. A. Hashim, Intech (2011).
V. Schettino and R. Bini, Chem. Soc. Rev. 36, 869 (2007).
W. Grochala et al., Agnew Chem Int. Ed., 46, 3620 (2007).
Y. Song, R. J. Hemley, H. K. Mao, and D. R. Herschbach, in ˇ°Chemistry under Extreme Conditionsˇ±, p189-222, ed. M.R. Manaa, Elsevier Science (2005).