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Title: Pressure induced polymerization of acetylide anions in CaC2 and 107 fold enhancement of electrical conductivity

Transformation between different types of carbon–carbon bonding in carbides often results in a dramatic change of physical and chemical properties. Under external pressure, unsaturated carbon atoms form new covalent bonds regardless of the electrostatic repulsion. It was predicted that calcium acetylide (also known as calcium carbide, CaC2) polymerizes to form calcium polyacetylide, calcium polyacenide and calcium graphenide under high pressure. In this work, the phase transitions of CaC2 under external pressure were systematically investigated, and the amorphous phase was studied in detail for the first time. Polycarbide anions like C66– are identified with gas chromatography-mass spectrometry and several other techniques, which evidences the pressure induced polymerization of the acetylide anions and suggests the existence of the polyacenide fragment. Additionally, the process of polymerization is accompanied with a 107 fold enhancement of the electrical conductivity. As a result, the polymerization of acetylide anions demonstrates that high pressure compression is a viable route to synthesize novel metal polycarbides and materials with extended carbon networks, while shedding light on the synthesis of more complicated metal organics.
Authors:
 [1] ;  [1] ;  [2] ;  [3] ;  [1] ;  [4] ;  [1] ;  [5] ;  [6] ;  [6] ;  [6] ;  [6] ;  [7] ;  [8] ;  [9] ;  [2] ;  [10]
  1. Center for High Pressure Science and Technology Advanced Research (HPSTAR), Beijing (China)
  2. Center for High Pressure Science and Technology Advanced Research (HPSTAR), Beijing (China); Carnegie Institution of Washington, Washington, D.C. (United States)
  3. COFCO Nutrition & Health Research Institute, Beijing (China)
  4. Agilent Technologies (China) Co., Ltd., Beijing (China)
  5. Durham Univ., Durham (United Kingdom)
  6. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  7. Center for High Pressure Science and Technology Advanced Research (HPSTAR), Beijing (China); Carnegie Institution of Washington, Washington, D.C. (United States); Carnegie Institution of Washington, Argonne, IL (United States)
  8. Carnegie Institution of Washington, Washington, D.C. (United States)
  9. Southern Univ. of Science and Technology, ShenZhen (China)
  10. Chinese Academy of Sciences (CAS), Beijing (China); Collaborative Innovation Centre of Quantum Matter, Beijing (China)
Publication Date:
OSTI Identifier:
1311295
Grant/Contract Number:
AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Chemical Science
Additional Journal Information:
Journal Name: Chemical Science; Journal ID: ISSN 2041-6520
Publisher:
Royal Society of Chemistry
Research Org:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences (CNMS); Spallation Neutron Source
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY