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Department of Chemistry Choong-Shik Yoo Group

Research Highlights, Projects, and Supports of the Yoo Group:

Recent Research Highlights:

Synthesis of reactive atomistic composites by compressing organometallic compounds: Read the paper by YoungJay Ryu, Minseob Kim, and Choong-Shik Yoo, Scientific Reports (2015) DOI:10.1038/srep15139.


In this paper, we presented the phase diagram of Fe(CO)5, consisting of three molecular polymorphs (phase I, II and III) and an extended polymeric phase that can be recovered at ambient condition. The phase diagram indicates a limited stability of Fe(CO)5 within a pressure-temperature dome formed below the liquid- phase II- polymer triple point at 4.2 GPa and 580 K. The limited stability, in turn, signifies the temperature-induced weakening of Fe-CO back bonds, which eventually leads to the dissociation of Fe-CO at the onset of the polymerization of CO. The recovered polymer is a composite of novel nm-lamellar layers of crystalline hematite Fe2O3 and amorphous carbon-oxygen polymers. These results, therefore, demonstrate the synthesis of Fe-doped CO polymer by compressing Fe(CO)5, which advocates a novel synthetic route to develop atomistic composite materials by compressing organometallic compounds

Discovery of High Energy Density, Layered Polymeric Nitrogen (LP-N) with colossal Raman intensity: Read the paper by D. Tomasino, M. Kim, J. Smith, and C. S. Yoo, Phys. Rev. Lett. 113, 205502 (2014)


This new paper reports a significant discovery of novel layered, singly-bonded polymeric nitrogen (LP-N), synthesized by laser-heating nitrogen molecules at pressures between 125-180 GPa. This new material exhibits a wide range of novel properties, including the colossal Raman cross section – presumably the largest of all solids, extremely high density (ro=4.0 g/cm3) even compared to diamond (3.5 g/cm3), high stiffness (Bo=345 GPa) rivaling superhard cubic-BN, and potentially high energy density exceeding its sister phase cg-N and five times of TNT. How many solids can have all these properties together? Not many, but only a few! It makes LP-N to join a class of novel materials like diamond and graphene, which can potentially lead to materials innovation in future. Importantly, the presence of LP-N also provides a new constraint for the nitrogen phase diagram, highlighting an unusual symmetry lowering 3D cg– to 2D LP-N transition, in contrast to more commonly found 2D to 3D transitions as in the graphite-to-diamond transition, and thereby the enhanced electrostatic contribution to the stabilization of this densely packed layer structure of LP-N.


Current Research Projects:

  • ARO: Dense Carbon-Organic Framework Solids in High Energy Density
  • NSF-DMR: Multifunctional Hybrid Carbon Networks
  • DTRA: Chemistry of Metal Plasma and Nuclear Forensics
  • DOD-NEEC: Network Polymers for Chemical Energy Depository
  • DOE-NNSA: Planetary Materials under Extreme Conditions
  • ACS-PRF: Formation and Evolution of Abiotic Hydrocarbons.
  • ARO: Dynamic Response of Reactive Metals.
  • DARPA: XSolids: Carbon Oxides
  • NSF-DMR: Squeezing Simple Molecules to Novel Conducting Polymers.
  • DTRA: High Energy Density Monolithic Organometallic Solids.
  • DCO/UCLA-Sloan: Physical and Chemical Behaviors of Earth’s Volatiles.
  • DHS: ALERT Center for Excellence.


Many thanks for the research supports by:



Mbar Chemistry:

The goal of this project is to investigate new states of matter and novel phenomena in low-Z solids and fluids occurring at Mbar (or ~million atmospheres) pressures. At these conditions, the compression energy (PDV) of molecular solids often exceeds a 10 eV/atom or 100 KJ/mol, rivaling those of the most stable chemical bonds (a few tens to hundreds KJ/mol)- certainly enough to induce bond scissions leading to chemical changes.  Materials often transform into more compact structures with itinerant electrons and often unexpected states of high energy-density, superionic, superconducting and superhard solids.  Therefore, our research efforts are centered at:

  • Discovery of new states of matter and novel phenomena
  • Understanding the governing rules for pressure-induced phase transitions
  • Exploiting fundamental understanding of materials meta/stabilities and collective behaviors of solids – critical issues in solid state transformations
  • Helping establish new Periodic orders of solids at Mbar pressures.


The research efforts related to Mbar Chemistry has been supported by:

  • NSF-DMR (0854618) on Mbar Chemistry: Novel States of Matter at Extreme Conditions
  • DARPA (20-XSolids-FP-001) on XSolids: Extended Carbon Oxides
  • DTRA (HDTRA1-09-1-0041): Novel Functional Extended Solids at Extreme Conditions


  • Phase diagram and transformation of iron pentacarbonyl to nm layered hematite and carbon- oxygen polymer under pressure, YoungJay Ryu, Minseob Kim, and Choong-Shik Yoo, Scientific Reports (2015) DOI:10.1038/srep15139.
  • Pressure-induced symmetry lowering transition in dense nitrogen to layered polymeric nitrogen (LP-N) with colossal Raman intensity, D. Tomasino, M. Kim, J. Smith, and C. S. Yoo, Phys. Rev. Lett. 113, 205502 (2014).
  • Transformation and Structure of Silicate-like CO2-V, Choong-Shik Yoo, Minseob Kim, Wolfgang Morgenroth, Peter Liermann, Phys. Rev. B. 87, 214103 (2013).
  • Physical and Chemical Transformations of Highly Compressed Carbon Dioxide at Bond Energies, Choong-Shik Yoo, Phys. Chem. Chem. Phys. 15, 7949 (2013).
  • Phase diagram of Carbon Dioxide: Update and Challenges, Choong-Shik Yoo, A. Sengupta, and Minseob Kim, High Pres. Res. 31, 68 (2011).
  • Novel 2D and 3D Extended Solids and Metallization of Compressed XeF2, Minseob Kim, Mathew Debessai, and Choong-Shik Yoo, Nature Chem. 2, 784 (2010).