Abstract
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. 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.
| Original language | English |
|---|---|
| Pages (from-to) | 298-304 |
| Number of pages | 7 |
| Journal | Chemical Science |
| Volume | 8 |
| Issue number | 1 |
| DOIs | |
| State | Published - 2016 |
| Externally published | Yes |
Funding
The authors acknowledge the support of NSAF (Grant No. U1530402) and NSFC (Grant No. 21501162). This work was supported as part of the Energy Frontier Research in Extreme Environment Center (Efree), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award DE-SC0001057. A portion of this research was performed at HPCAT (Sector 16), Advanced Photon Source (APS), Argonne National Laboratory. HPCAT (Geophysical Lab) operations are supported by DOE-NNSA under Award No. DE-NA0001974 and DOE-BES under Award No. DE-FG02-99ER45775, with partial instrumentation funding by NSF. APS is supported by DOE-BES, under Contract No. DE-AC02-06CH11357. A portion of this research was conducted at the Center for Nanophase Materials Sciences and Spallation Neutron Source, which are sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. The authors thank Dr Antonio F. Moreira dos Santos for the help in the neutron diffraction experiment, Dr Hongping Yan for the help in the in situ XRD experiment and Dr George Cody for valuable discussion. SNAP pressure cells were used to synthesize many of the in situ and ex situ samples used in this study. Work at IOPCAS was supported by NSF and MOST through research projects. The authors thank Agilent Technologies (China), Inc. for assistance in the GC-MS experiment. The metadynamic calculations were performed at Tianhe II in Guangzhou which is supported by Special Program for Applied Research on Super Computation of the NSFC-Guangdong Joint Fund (the second phase).
| Funders | Funder number |
|---|---|
| DOE-BES | DE-FG02-99ER45775 |
| DOE-NNSA | DE-NA0001974 |
| Energy Frontier Research in Extreme Environment Center | |
| Scientific User Facilities Division | |
| Special Program for Applied Research on Super Computation of the NSFC-Guangdong Joint Fund | |
| National Science Foundation | DE-AC02-06CH11357 |
| U.S. Department of Energy | |
| Agilent Technologies | |
| Office of Science | |
| Basic Energy Sciences | DE-SC0001057 |
| Argonne National Laboratory | |
| Oak Ridge National Laboratory | |
| National Natural Science Foundation of China | 21501162 |
| Ministry of Science and Technology of the People's Republic of China | |
| National Safety Academic Fund | U1530402 |