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?
Pressure 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?
Gases 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?
Diamond 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?
Materials 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 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?
Pressure tuning of functional materials for energy devices
Development of chemical energy storage materials
Structural tuning & gas storage in porous materials
Pressure 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. 
Gases 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.
Diamond 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. 
Materials 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 3